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Results: 21 - 40of11002
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- Article
Enhanced OER Performance through Electronic Structure Engineering in Artificial LaNiO3/SrRuO3 Superlattices
Jiale Han - ,
Jinrui Guo - ,
Huan Liu - ,
Yue Han - ,
Jiaqing Wang - ,
Xiaoqiao Ma - ,
Bixing Yan - ,
Bin He *- , and
Weiming Lü *
The Journal of Physical Chemistry C 2024, 128, 3, 1116-1121 (C: Chemical and Catalytic Reactivity at Interfaces)Publication Date (Web):January 11, 2024DOI: 10.1021/acs.jpcc.3c08070Your access to this publication has been provided by Learn More
ABSTRACTThe engineering of the electronic structure in transition metal oxide (TMO) catalysts has emerged as a promising approach to enhance the oxygen evolution reaction (OER) in water-splitting, achieved through precise modulation of the absorption and desorption energies of water intermediates. Among various strategies, strain-induced tunability in electronic structures has shown great potential to significantly improve the performance of the OER performance. In this study, we utilized artificial superlattices (LaNiO3)n/(SrRuO3)m (LNOn/SROm) to optimize the surface orbital occupancy of LNO and maximize the strain effect’s effectiveness. Our findings indicate that, compared to single-layer LNO films, the LNO1/SRO2 superlattice exhibits an impressive 28% reduction in Tafel slope, along with an approximately 315% enhancement in catalytic current density at 1.65 V for the OER process. The approach of the 3dx2‐y2 orbital of eg toward the 2p orbital by strain in superlattice is responsible for this OER enhancement, where the centering of eg and 2p orbitals is improved. Our results not only provide a promising strategy for the enhanced OER by engineering the TMO’s surface electronic structure, but also showcase the exceptional design of OER catalysts using artificial TMO superlattices.
- Article
Single Atoms on a Nitrogen-Doped Boron Phosphide Monolayer: A New Promising Bifunctional Electrocatalyst for ORR and OER
Hanghang Zeng - ,
Xinyi Liu - ,
Fengbo Chen - ,
Zhiguo Chen - ,
Xiaoli Fan *- , and
Woonming Lau *
ACS Applied Materials & Interfaces 2020, 12, 47, 52549-52559 (Energy, Environmental, and Catalysis Applications)Publication Date (Web):November 10, 2020DOI: 10.1021/acsami.0c13597Your access to this publication has been provided by Learn More
ABSTRACTEfficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional electrocatalysts have been pursued for decades. Meanwhile, single metal atoms embedded in a two-dimensional material substrate (2D-substrate) have emerged as an outstanding catalyst. Herein, we report on computational ORR/OER efficiencies of a series of single atom catalyst systems, with a nitrogen-doped boron phosphide monolayer (N3-BP) as the 2D-substrate, and with Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Rh, Pd, Ir, and Pt as the single-atom subject (M). In brief, our density functional theory results show that the overpotentials for ORR/OER are low for CoN3-BP, NiN3-BP, and PtN3-BP, with {ηORR; ηOER} of {0.36; 0.42 V}, {0.29; 0.44 V}, and {0.32; 0.25 V}, respectively. The relevant attributes such as the chemical stability of the 2D-substrate in the ORR/OER environments, immobilization of the single-atom subject on the 2D-substrate, and mechanisms of the ORR/OER activity and the catalyst recovery on the MN3-BP catalysts were carefully examined. The key to the comparative study is how the electronic states of the reaction center near the Fermi level of the catalytic system match the frontier orbitals of ORR/OER reaction intermediates. In short, our method predicts the ORR/OER catalytic efficiencies of novel catalysts via a single-atom/2D-substrate design strategy.
- Article
A Comprehensive Pyrolysis Mechanism of Binuclear Chromium-Based Complexes for Superior OER Activity
Meixing Gan - ,
Li Li - ,
Xixian Yang - ,
Hongwei Rong - ,
Zheng Wang - ,
Yuebin Li - ,
Yuexing Zhang *- ,
Xueli Chen *- , and
Xu Peng *
ACS Applied Materials & Interfaces 2024, 16, 22, 28664-28672 (Energy, Environmental, and Catalysis Applications)Publication Date (Web):May 24, 2024DOI: 10.1021/acsami.4c04688Your access to this publication has been provided by Learn More
ABSTRACTTransition metal oxides are widely pursued as potent electrocatalysts for the oxygen evolution reaction (OER). However, single-metal chromium catalysts remain underexplored due to their intrinsic activity limitations. Herein, we successfully synthesize mixed-valence, nitrogen-doped Cr2O3/CrO3/CrN@NC nanoelectrocatalysts via one-step targeted pyrolysis techniques from a binuclear Cr-based complex (Cr2(Salophen)2(CH3OH)2), which is strategically designed as a precursor. Comprehensive pyrolysis mechanisms were thoroughly delineated by using coupled thermogravimetric analysis and mass spectrometry (TG–MS) alongside X-ray diffraction. Below 800 °C, the generation of a reducing atmosphere was noted, while continuous pyrolysis at temperatures exceeding 800 °C promoted highly oxidized CrO3 species with an elevated +6 oxidation state. The optimized catalyst pyrolyzed at 1000 °C (Cr2O3/CrO3/CrN@NCs-1000) demonstrated remarkable OER activity with a low overpotential of 290 mV in 1 M KOH and excellent stability. Further density functional theory (DFT) calculations revealed a much smaller reaction energy barrier of CrO3 than the low oxidation state species for OER reactivity. This work reveals fresh strategies for rationally engineering chromium-based electrocatalysts and overcoming intrinsic roadblocks to enable efficient OER catalysis through a deliberate oxidation state and compositional tuning.
- Article
In Situ Construction of Bifunctional N-Doped Carbon-Anchored Co Nanoparticles for OER and ORR
Xi-Zheng Fan - ,
Xin Du - ,
Qing-Qing Pang - ,
Shuo Zhang - ,
Zhong-Yi Liu *- , and
Xin-Zheng Yue *
ACS Applied Materials & Interfaces 2022, 14, 6, 8549-8556 (Surfaces, Interfaces, and Applications)Publication Date (Web):February 7, 2022DOI: 10.1021/acsami.1c21445Your access to this publication has been provided by Learn More
ABSTRACTDesigning highly active and more durable oxygen electrocatalysts for regenerative metal-air batteries and water splitting is of practical significance. Herein, an advanced Co/N–C-800 catalyst composed of abundant Co–Nx structures and carbon defects derived from cobalt phthalocyanine is synthesized. Remarkably, this catalyst exhibits favorable catalytic performance toward the oxygen evolution reaction (OER) with a receivable overpotential of 274 mV in an alkaline medium achieving a current density of 10 mA cm–2 and a Tafel slope of 43.6 mV decade–1, outperforming the commercial RuO2 catalyst. It further displays a high half-wave potential (0.82 V) for the oxygen reduction reaction in 0.1 M KOH. Theoretical calculations reveal that the Co–Nx active sites along with the carbon defects can decrease the adsorption energy of intermediates (OH*, O*, and OOH*) and enhance the electron-transfer ability, thus boosting the OER process.
- Article
Fe3C@C/CNT Hybrids Derived from Catalytic Pyrolysis of Lignite: Electrocatalysts for OER
Xiao Liu - ,
Hongwei Liu - ,
Liang Lv - ,
Yongzhen Wang *- , and
Jun Liu *
Energy & Fuels 2023, 37, 17, 13260-13270 (Catalysis and Kinetics)Publication Date (Web):August 15, 2023DOI: 10.1021/acs.energyfuels.3c01711Your access to this publication has been provided by Learn More
ABSTRACTUsing lignite as the raw material to prepare a new OER catalyst, and thus to make high-value use of lignite and to meet the research and development needs for new energy materials at the same time, a novel Fe/Fe3C active species has been reported as a promising catalyst to replace precious metals. In this study, we developed a facile method for the preparation of Fe3C@C/CNT hybrid materials by catalytic pyrolysis of lignite using KOH and FeCO3. The structural characteristic of Fe3C@C/CNT hybrid materials is that Fe3C nanoparticles are encapsulated in carbon layers and carbon nanotubes, forming a special core–shell structure. The prepared materials have good graphitization and a large specific surface area (957 m2 g–1). We discussed the effects of KOH, FeCO3, and melamine in the catalytic pyrolysis of lignite to produce Fe3C@C/CNT materials: (1) Lignite can be catalyzed by KOH to generate carbon nanotubes and porous structures. (2) The transformation of carbon matrix to graphitic carbon is catalyzed and the Fe source for Fe3C is provided by FeCO3. (3) The aggregation of Fe into large and irregular Fe nanoparticles is inhibited by melamine, which facilitates the generation of Fe3C. When the Fe3C@C/CNT hybrid is used as an OER catalyst, the OER overpotential is only 407 mV at a current density of 10 mA cm–2 in an alkaline electrolyte, which has great application potential. This work is conducive to improving the economic benefits of lignite and provides a new idea for the high value-added utilization of lignite.
- Article
Theoretical Inspection of M1/PMA Single-Atom Electrocatalyst: Ultra-High Performance for Water Splitting (HER/OER) and Oxygen Reduction Reactions (OER)
Shamraiz Hussain Talib - ,
Zhansheng Lu *- ,
Xiaohu Yu - ,
Khalil Ahmad - ,
Beenish Bashir - ,
Zongxian Yang - , and
Jun Li *
ACS Catalysis 2021, 11, 14, 8929-8941 (Research Article)Publication Date (Web):July 7, 2021DOI: 10.1021/acscatal.1c01294Your access to this publication has been provided by Learn More
ABSTRACTDeveloping a cost-effective and highly efficient electrocatalyst with superior catalytic activity is crucial for clean and green water splitting, including the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR). The single-atom catalyst (SAC) is a breakthrough in industrial catalysis because of the advantages of maximum metal atom utilization, single active sites, strong metal–support interactions, and great potential to accomplish high catalytic performance and selectivity. Herein, we investigate the electrocatalytic performance of a series of SACs supported on a phosphomolybdic acid (PMA) cluster for the HER, OER, and ORR by using first-principles-based calculations. It has been found that the most plausible binding site for the single-metal adatoms is the 4-fold hollow (4H) site over the PMA cluster. Due to the higher stability and catalytic activity of single-metal adatoms, fast electron transfer kinetics is permissible through catalysis. Mainly, Pt1/PMA, Ru1/PMA, V1/PMA, and Ti1/PMA realized decent catalytic performance toward the HER due to nearly ideal (ΔGH* = 0) ΔGH* values via the Volmer–Heyrovsky pathway. The Co1/PMA (0.45 V) and Pt1/PMA (0.49 V) can be active and selective catalysts for the OER with their overpotentials comparable those of to MoC2, IrO2, and RuO2. Among the considered candidates, a non-noble metal Fe1/PMA SAC is a promising electrocatalyst for the ORR with an overpotential of 0.42 V, which is lower than that for the most favorable Pt (0.45 V) catalyst. Furthermore, Pt1/PMA is an auspicious multifunctional electrocatalyst for overall water splitting (−0.02 V for the HER and 0.49 V for the OER) and a metal-air battery (0.79 V for the ORR) catalyst. The current study is further extended to calculate the kinetic potential energy barrier for the excellent catalytic performance of Co1 for the OER and Fe1 for the ORR. The results suggest that the kinetic activation barrier values in all proton-coupled electron transfer steps are in good agreement with the thermodynamic results. It was revealed that the PMA cluster is a promising single-atom support for the HER, OER, and ORR and provides low-cost and highly efficient electrocatalytic activity under normal reaction conditions.
- Article
Lanthanides Regulated the Amorphization–Crystallization of IrO2 for Outstanding OER Performance
Chenglong Ma - ,
Wei Sun - ,
Waqas Qamar Zaman - ,
Zhenhua Zhou - ,
Hao Zhang - ,
Qicheng Shen - ,
Limei Cao - , and
Ji Yang *
ACS Applied Materials & Interfaces 2020, 12, 31, 34980-34989 (Energy, Environmental, and Catalysis Applications)Publication Date (Web):July 13, 2020DOI: 10.1021/acsami.0c08969Your access to this publication has been provided by Learn More
ABSTRACTResearch has been focused on regulating the amorphous surface of Ir-based materials to achieve a higher oxygen evolution reaction (OER) activity. The IrOx amorphous layer is generally considered to be substantial enough to break the limitation created by the conventional adsorbate evolution mechanism (AEM) in acidic media. In this work, we used lanthanides to regulate IrOx amorphization–crystallization through inhibiting the crystallization of iridium atoms in the calcination process. The chosen route created abundant crystalline–amorphous (c-a) interfaces, which greatly enhanced the charge transfer kinetics and the stability of the materials. The mass activity of iridium in the synthesized IrO2@LuIr1–nOx(OH)y structure reached 128.3 A/gIr, which is 14.6-fold that of the benchmark IrO2. All the IrO2@LnIr1–nOx(OH)y (Ln = La–Lu) structures reflected 290–300 mV of overpotential at 10 mA/cmgeo2. We demonstrate that a highly active c-a interface possesses an efficient charge transfer capability and is conducive to the stability of the activated oxygen species. The surface-activated oxygen species and the tensile strain [IrO6] octahedron regulated by lanthanides are synergistically beneficial for increasing the intrinsic OER activity. Our research findings introduce c-a interface generation by the regulation of lanthanides as a new method for the rational design of robust OER catalysts.
- Article
Adsorption and On-Site Transformation of Transition Metal Cations on Ni-Doped AlOOH Nanoflowers for OER Electrocatalysis
Yao Zhou - and
Hua Chun Zeng *
ACS Sustainable Chemistry & Engineering 2019, 7, 6, 5953-5962 (Research Article)Publication Date (Web):February 14, 2019DOI: 10.1021/acssuschemeng.8b06020Your access to this publication has been provided by Learn More
ABSTRACTAlOOH has long been used as excellent adsorbent for removal of heavy metal cations from wastewater. Herein we report one-pot synthesis of carboxylic-functionalized Ni-doped AlOOH nanoflowers (AlOOH NFs) with high adsorptive capability toward various transition metal cations, and more importantly, the AlOOH NFs adsorbed with various transition metal cations were for the first time directly used as electrocatalyst for oxygen evolution reaction (OER). By simply manipulating the initial metal cation concentration and their molar ratio, the OER catalytic performance of the resulting catalysts could be modulated. The lowest overpotential at a current density of 10 mA cm–2 prepared from AlOOH NFs adsorbed with FeIII and NiII is 0.32 V in 0.1 M KOH and 0.275 V in 1.0 M KOH. Such AlOOH-supported electrocatalyst demonstrates remarkable stability, which shows no evident increase of the overpotential at 10 mA cm–2 after 2 h of steady electrolysis at an overpotential of 0.42 V. The excellent OER electrocatalytic activity originates from the on-site formation of ultrafine FeOOH and NiOOH nanoclusters with average sizes below 3 nm during the electrocatalytic process. As such, we demonstrate the workability of using functionalized AlOOH NFs as a bifunctional platform for adsorption of transition metal cations and easy preparation of efficient and cost-effective OER catalysts.
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Fe-MOF-Derived Efficient ORR/OER Bifunctional Electrocatalyst for Rechargeable Zinc–Air Batteries
Yun-Wu Li - ,
Wen-Jie Zhang - ,
Jing Li - ,
Hui-Yan Ma - ,
Hong-Mei Du - ,
Da-Cheng Li - ,
Su-Na Wang *- ,
Jin-Sheng Zhao *- ,
Jian-Min Dou - , and
Liqiang Xu *
ACS Applied Materials & Interfaces 2020, 12, 40, 44710-44719 (Energy, Environmental, and Catalysis Applications)Publication Date (Web):September 9, 2020DOI: 10.1021/acsami.0c11945Your access to this publication has been provided by Learn More
ABSTRACTThe construction of an efficient oxygen reduction reaction and oxygen evolution reaction (ORR/OER) bifunctional electrocatalyst is of great significance but still remains a giant challenge for high-performance metal–air batteries. In this study, uniform FeS/Fe3C nanoparticles embedded in a porous N,S-dual doped carbon honeycomb-like composite (abbr. FeS/Fe3C@NS-C-900) have been conveniently fabricated by pyrolysis of a single-crystal Fe-MOF, which has a low potential gap ΔE of ca. 0.72 V, a competitive power density of 90.9 mW/cm2, a specific capacity as high as 750 mAh/gZn, and excellent cycling stabilities over 865 h (1730 cycles) at 2 mA/cm2 when applied as a cathode material for rechargeable zinc–air batteries. In addition, the two series-linked Zn–air batteries successfully powered a 2.4 V LED light as a real power source. The efficient ORR/OER bifunctional electrocatalytic activity and long-term durability of the obtained composite might be attributed to the characteristic honeycomb-like porous structure with sufficient accessible active sites, the synergistic effect of FeS and Fe3C, and the N,S codoped porous carbon, which provides a promising application potential for portable electronic Zn–air battery related devices.
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Self-Supported CdP2–CDs–CoP for High-Performance OER Catalysts
Yu Bai - ,
Long−Cheng Zhang - ,
Qiulin Li - ,
Yuanke Wu - ,
Youpeng Wang - ,
Maowen Xu - , and
Shu−Juan Bao *
ACS Sustainable Chemistry & Engineering 2021, 9, 3, 1297-1303 (Research Article)Publication Date (Web):January 11, 2021DOI: 10.1021/acssuschemeng.0c07700Your access to this publication has been provided by Learn More
ABSTRACTDesigning low-cost and high-activity electrocatalysts is significant to enhance the slow kinetic process of oxygen evolution reaction (OER). Inspired by the Lego game, hierarchical CdP2–CDs–CoP nanoarrays were fabricated by combining negatively charged carbon quantum dots (CDs) with positively charged Co and Cd ions. Because of the low evaporation temperature of Cd and relatively high solubility product (Ksp) of Cd(OH)2, trace CdP2 is trapped on the surface of CdP2–CDs–CoP nanoarrays. When coupled with CDs, CdP2 enriches the defects and active sites of catalysts. The CdP2–CDs–CoP nanoarray, as a robust OER electrocatalyst, delivers an overpotential of 285 mV to drive a current density of 10 mA cm–2, demonstrating its superiority over commercial RuO2.
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Oxygen Evolution Reaction (OER) on Clean and Oxygen Deficient Low-Index SrTiO3 Surfaces: A Theoretical Systematic Study
Mengsi Cui - ,
Taifeng Liu *- ,
Qiuye Li - ,
Jianjun Yang - , and
Yu Jia *
ACS Sustainable Chemistry & Engineering 2019, 7, 18, 15346-15353 (Research Article)Publication Date (Web):August 14, 2019DOI: 10.1021/acssuschemeng.9b02672Your access to this publication has been provided by Learn More
ABSTRACTSrTiO3 (STO) is a widely used photocatalyst for water splitting, which has no photoactivity without a cocatalyst. The reason for this unclear. Here, we performed an oxygen evolution reaction (OER) on clean and oxygen deficient (100), (110), and (111) surfaces on STO by density functional theory. Combining our results with experimental results in the literature, we demonstrated that the overpotential is small enough for OER to occur on (100) surfaces. There is no photoactivity due to the photogenerated holes that cannot migrate to the (100) surfaces. On the (110) and (111) surfaces, the overpotential is very high, which prevents the OER from taking place on these two surfaces. Our work gives a guidance principle to understand the water splitting from the overpotential of OER and migrating photogenerated carriers. It may be helpful to design high efficiency photocatalysts based on STO.
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Boosting the OER Performance of Nitrogen-Doped Ni Nanoclusters Confined in an Amorphous Carbon Matrix
Ting Yu - ,
Yinhui Hou - ,
Ping Shi - ,
Yong Yang *- ,
Mingyue Chen - ,
Wenda Zhou - ,
Zhenzhen Jiang - ,
Xingfang Luo *- ,
Hang Zhou - , and
Cailei Yuan *
Inorganic Chemistry 2022, 61, 4, 2360-2367 (Article) 重试 错误原因Publication Date (Web):January 19, 2022DOI: 10.1021/acs.inorgchem.1c03780Your access to this publication has been provided by Learn More
ABSTRACTNanoclusters are ideal electrocatalysts due to their high surface activity. However, their high activities also lead to serious agglomeration and performance attenuation during the catalytic process. Here, highly dispersed Ni nanoclusters (∼3 nm) confined in an amorphous carbon matrix are successfully fabricated by pulsed laser deposition, followed by rapid temperature annealing treatment. Then, the Ni nanoclusters are further doped with nitrogen element through a clean N2 radio frequency plasma technology. It is found that the nitrogen-doped Ni nanoclusters obtained under optimized conditions showed superior OER performance with a very low overpotential of 240 mV at a current density of 10 mA/cm2, together with good stability. The excellent OER performance of the nanoclusters can be attributed to the unique confined structure and nitrogen doping, which not only provide more active sites but also improve the conductivity. Our work provides a controllable method for the construction of a novel confined structure with controllable nitrogen doping, which can be used as a high-efficiency OER electrocatalyst.
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Metal–Support Interaction Can Deactivate IrOx/Sb:SnO2 OER Catalysts in Polyol Process
Hansaem Jang - ,
Jeong-Hyeon Lee - ,
Jeon Ryang Lee - , and
Tae-Won Kim *
ACS Applied Energy Materials 2022, 5, 8, 9297-9302 (Letter)Publication Date (Web):August 11, 2022DOI: 10.1021/acsaem.2c01765Your access to this publication has been provided by Learn More
ABSTRACTOnly a few materials can remain undissolved under working conditions for the oxygen evolution reaction (OER) in acidic media, which limits the choice of catalysts and supports. One of the practical catalyst/support candidates is IrOx/Sb:SnO2 (Ir/ATO) because both components are thermodynamically stable under low-pH anodic conditions. Moreover, between Ir and ATO, a strong metal–support interaction is present, thereby allowing for long-lasting OER activity unless the support degrades. However, we demonstrate that the strong interaction can paradoxically deactivate Ir/ATO structures when synthesizing them using the polyol process. We reveal that the strong interaction in the presence of polyol at elevated temperatures can cause the reduction of the Sb dopant to zero-valency. Findings show that the varied oxidation state of the dopant decreases the electrical conductivity of the Ir/ATO, impeding the electron transfer through the support, hence deteriorating electrocatalytic activity toward the OER.
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Effects of Alternating Magnetic Fields on the OER of Heterogeneous Core–Shell Structured NiFe2O4@(Ni, Fe)S/P
Yuan-li Wang - ,
Tong-hui Yang - ,
Song Yue - ,
Hang-bo Zheng - ,
Xiao-pan Liu - ,
Peng-zhao Gao *- ,
Hang Qin - , and
Han-ning Xiao
ACS Applied Materials & Interfaces 2023, 15, 9, 11631-11641 (Energy, Environmental, and Catalysis Applications)Publication Date (Web):February 28, 2023DOI: 10.1021/acsami.2c16656Your access to this publication has been provided by Learn More
ABSTRACTComposition optimization, structural design, and introduction of external magnetic fields into the catalytic process can remarkably improve the oxygen evolution reaction (OER) performance of a catalyst. NiFe2O4@(Ni, Fe)S/P materials with a heterogeneous core–shell structure were prepared by the sulfide/phosphorus method based on spinel-structured NiFe2O4 nanomicrospheres. After the sulfide/phosphorus treatment, not only the intrinsic activity of the material and the active surface area were increased but also the charge transfer resistance was reduced due to the internal electric field. The overpotential of NiFe2O4@(Ni, Fe)P at 10 mA cm–2 (iR correction), Tafel slope, and charge transfer resistance were 261 mV, 42 mV dec–1, and 3.163 Ω, respectively. With an alternating magnetic field, the overpotential of NiFe2O4@(Ni, Fe)P at 10 mA cm–2 (without iR correction) declined by 45.5% from 323 mV (0 mT) to 176 mV (4.320 mT). Such enhancement of performance is primarily accounted for the enrichment of the reactive ion OH– on the electrode surface induced by the inductive electric potential derived from the Faraday induction effect of the AMF. This condition increased the electrode potential and thus the charge transfer rate on the one hand and weakened the diffusion of the active substance from the electrolyte to the electrode surface on the other hand. The OER process was dominantly controlled by the charge transfer process under low current conditions. A fast charge transfer rate boosted the OER performance of the catalyst. At high currents, diffusion exerted a significant effect on the OER process and low OH– diffusion rates would lead to a decrease in the OER performance of the catalyst.
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Unfolding the Electrocatalytic Efficiency of Ultrastable CoFeLDH Nanorods by Creating Oxygen Vacancies for OER
Krishankant - ,
Aashi - ,
Ayushi Jain - ,
Jatin Sharma - ,
Rekha Rani - ,
Chandan Bera - , and
Vivek Bagchi *
ACS Applied Energy Materials 2024, 7, 3, 1027-1036 (Article)Publication Date (Web):January 12, 2024DOI: 10.1021/acsaem.3c02468Your access to this publication has been provided by Learn More
ABSTRACTHarnessing the potential of oxygen vacancies (Ov) in metal oxides presents a promising avenue for expediting reaction kinetics in water oxidation. In this context, layered double hydroxides (LDH) offer a versatile platform for developing cost-effective electrocatalysts with exceptional performance, thanks to their distinctive lamellar morphology. In this study, we unveil the augmented electrochemical efficiency of CoFeLDH by deliberately inducing an optimal oxygen vacancy (Ov) under ambient conditions for the oxygen evolution reaction (OER). The transformation of CoFeLDH nanorods (CoFeLDH) into Ov-rich CoFeLDH (CoFeLDH-Ov) takes place through a chemical reduction process at room temperature. The effect of Ov within the catalyst is substantiated through qualitative analyses, such as X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), and electron paramagnetic resonance (EPR). The resulting catalyst, CoFeLDH-Ov, exhibits an overpotential of 220 mV at a current density of 30 mA/cm2 in a 1 M KOH electrolyte, indicating an enhanced electroactivity when compared to CoFeLDH (without Ov defects). The catalyst also reveals excellent stability for more than 500 h at a higher current density of 50 mA/cm2. To validate the catalyst’s conducive nature, density functional theory (DFT) calculations are performed, revealing iron (Fe) as the prominent active site within the catalyst. By means of comprehensive experimental and theoretical analyses, the substantial influence of Ov on the electronic structure of the LDH system is demonstrated, which, in turn, facilitates facile charge transfer and strengthens the efficiency of the oxygen evolution reaction (OER).
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Tuning the Surface Electronic Structure of Amorphous NiWO4 by Doping Fe as an Electrocatalyst for OER
Hariharan N. Dhandapani - ,
Ragunath Madhu - ,
Aditi De - ,
Mohamed A. Salem - ,
B. Ramesh Babu *- , and
Subrata Kundu *
Inorganic Chemistry 2023, 62, 30, 11817-11828 (Article) 重试 错误原因Publication Date (Web):July 12, 2023DOI: 10.1021/acs.inorgchem.3c01095Your access to this publication has been provided by Learn More
ABSTRACTWater electrolysis is considered as one of the alternative potential approaches for producing renewable energy. Due to the sluggish kinetic nature of oxygen evolution reaction (OER), it encounters a significant overpotential to achieve water electrolysis. Hence, the advancement of cost-effective transition metal-based catalysts toward water splitting has gained global attention in recent years. In this work, the doping of Fe over amorphous NiWO4 increased the OER activity effectively and achieved stable oxygen evolution in the alkaline medium, which show better electrocatalytic activity as compared to crystalline tungstate. As NiWO4 has poor activity toward OER in the alkaline medium, the doping of Fe3+ will tune the electronic structure of Ni in NiWO4 and boost the OER activity. The as-synthesized Fe-doped amorphous NiWO4 exhibits a low overpotential of 230 mV to achieve a current density of 10 mA cm–2 and a lower Tafel slope value of 48 mV dec–1 toward OER in 1.0 M KOH solution. The catalyst also exhibits long-term static stability of 30 h during chronoamperometric study. The doping of Fe improves the electronic conductivity of Ni-3d states in NiWO4 which play a dominant role for better catalytic activity via synergistic interaction between Fe and active Ni sites. In future, these results offer an alternative route for precious metal-free catalysts in alkaline medium and can be explicitly used in various tungstate-based materials to increase the synergism between the doped atom and metal ions in tungstate-based materials for further improvement in the electrocatalytic performance.
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Effect of IrO6 Octahedron Distortion on the OER Activity at (100) IrO2 Thin Film
Gaëtan Buvat - ,
Mohammad J. Eslamibidgoli - ,
Azza Hadj Youssef - ,
Sébastien Garbarino - ,
Andreas Ruediger - ,
Michael Eikerling - , and
Daniel Guay *
ACS Catalysis 2020, 10, 1, 806-817 (Research Article)Publication Date (Web):December 4, 2019DOI: 10.1021/acscatal.9b04347Your access to this publication has been provided by Learn More
ABSTRACTThe (100) crystallographic plane is the most active facet of iridium dioxide (IrO2) for the oxygen evolution reaction (OER). Pulsed laser deposition was used to grow (100) IrO2 on a (100) SrTiO3 substrate at deposition temperature ranging from room temperature to 600 °C. Detailed structural and morphological characterization was performed using AFM, XRD, and X-ray reciprocal space mapping (RSM) to unravel the geometrical arrangement of [IrO6] octahedra in the (100) IrO2 thin films. It is shown that the symmetry mismatch between the substrate and the epitaxial thin film imposed an orthorhombic distortion of the tetragonal structure of IrO2 and, as a consequence, the [IrO6] geometry is distorted. These data were correlated to the OER characteristics established from electrochemical measurements. DFT modeling was employed to relate differences in surface relaxation of IrO2 films prepared at different temperatures with changes in OER activity. Vacancy formation leads to higher surface stability at temperatures around 500 °C, which corresponds to the deposition temperature at which the electrocatalytic activity of (100) epitaxial IrO2 film is maximal.
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Substantial Impact of Spin State Evolution in OER/ORR Catalyzed by Fe–N–C
Mingyuan Yu - ,
Ang Li *- ,
Erjun Kan *- , and
Cheng Zhan *
ACS Catalysis 2024, 14, 9, 6816-6826 (Research Article)Publication Date (Web):April 18, 2024DOI: 10.1021/acscatal.3c06122Your access to this publication has been provided by Learn More
ABSTRACTThe Fe-embedded N-doped graphene (Fe–N–C) is the most representative single atom catalyst (SAC) that has shown great potentiality in electrocatalysis, such as oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the active moiety of Fe–N–C is still elusive due to contradictory experimental results. Moreover, early simulations mainly focus on the thermodynamic potential of adsorbates, while the effect of spin multiplicity receives little attention. To explore the role of spin multiplicity in electrocatalysis, we employ the constant-potential density functional theory (DFT) to systematically study the structural evolution of the high-spin (HS) and intermediate-spin (IS) FeN4 site (marked by FeN4HS/IS) in OER and ORR processes. With the consideration of spin multiplicity, our simulation shows spontaneous oxidation from Fe(II)N4IS to Fe(III)N4HS at potential U = 0.4 V versus SHE. Further simulation indicates that the FeN4IS site undergoes a sequential adsorption of *OH and *OOH along with U increase, which leads to the spin state transition from IS to HS. According to the constant-potential free energy analysis, the FeN4HS*OOH is confirmed to be the practical active centers of OER, while the FeN4HS*OH and FeN4IS are assigned to the active center of ORR in low and high overpotentials. The predicted ORR activity of FeN4HS*OH agrees with the in situ X-ray absorption near-edge spectroscopy (XANES) and 57Fe Mössbauer spectroscopy measurement by Xiao et al. [Microporous Framework Induced Synthesis of Single-Atom Dispersed Fe-NC Acidic ORR Catalyst and its In Situ Reduced Fe-N4 Active Site Identification Revealed by X-Ray Absorption Spectroscopy. ACS Catal. 2018, 8, 2824–2832]. Based on the geometry and orbital analysis, the bond length of Fe–N and coordination number of Fe center are found to have a significant impact on the d orbital splitting energy and thus induce the turnover of HS/IS stability in the OER/ORR intermediates. Our study brings comprehensive insights into the evolution of coordination and spin state in Fe–N–C, which reveals the significance of spin multiplicity in electrocatalysis and benefits further theoretical design of SACs from the perspective of spin effects.
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Crystalline Disorder, Surface Chemistry, and Their Effects on the Oxygen Evolution Reaction (OER) Activity of Mass-Produced Nanostructured Iridium Oxides
Raghunandan Sharma *- ,
Martin Aaskov Karlsen - ,
Per Morgen - ,
Jessica Chamier - ,
Dorthe Bomholdt Ravnsbæk - , and
Shuang Ma Andersen *
ACS Applied Energy Materials 2021, 4, 3, 2552-2562 (Article)Publication Date (Web):February 24, 2021DOI: 10.1021/acsaem.0c03127Your access to this publication has been provided by Learn More
ABSTRACTIn the present study, three mass-produced commercial IrOx samples from different suppliers were studied to establish correlations between various properties and their OER activities. The structures of the electrocatalysts at different scales were explored through laboratory instrumentation, powder X-ray diffraction, and synchrotron-based X-ray total scattering experiments combined with pair distribution function analysis. X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy using a transmission electron microscope were used to determine respectively the surface and the bulk elemental compositions of the samples. The coherent domain size (CDS) values of IrOx phases within the catalyst particles were estimated to be ∼10, ∼ 19, and ∼ 54 Å for the three IrOx samples. Surprisingly, the sample with a CDS of ∼19 Å turned out as the best OER electrocatalyst among the three in terms of mass-specific activity, IOER(m), followed by the 10 and 54 Å species. The amount of surface native compound oxygen was found to be a key parameter for the interface electrochemical accessibility. The intrinsic OER activity, evaluated using area-specific activity, IOER(a), suggests that the oxide with lattice disorder presenting a mixture of tetragonal and orthorhombic phases (70:20 w/w) is of superior intrinsic OER activity; however, the oxide with the presence of a monoclinic-like phase is of inferior intrinsic OER activity, which may also be due to the surface presence of Ir3+ along with Ir4+. The classic belief that the pure tetragonal phase is the best crystalline structure as the OER catalyst is challenged. Iridium oxides with disordered crystallinities may offer a class of highly active oxygen evolution electrocatalysts. The knowledge thus obtained should have a significant impact on the understanding, selection, and processing of IrOx-based OER electrocatalysts.
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Bifunctional OER/NRR Catalysts Based on a Thin-Layered Co3O4–x/GO Sandwich Structure
Yu Sun *- ,
Qiao Wang - , and
Zhongyuan Liu
ACS Applied Materials & Interfaces 2022, 14, 38, 43508-43516 (Functional Inorganic Materials and Devices)Publication Date (Web):September 15, 2022DOI: 10.1021/acsami.2c11674Your access to this publication has been provided by Learn More
ABSTRACTDue to ample low-coordinated surface atoms, a distorted lattice endows thin-layered transition metal oxides with a flexible electronic structure, making them the ideal candidates for overall ammonia synthesis. This work proposes a novel and facile method for the controllable synthesis of thin-layered Co3O4 catalysts with graphene as a conductive matrix to further enhance the overall N2 fixation performance. X-ray photoelectron spectroscopy (XPS) and synchrotron radiation X-ray absorption spectroscopy (XAS) demonstrate that the sandwiched Co3O4–x/GO catalysts enable exposure of more coordination unsaturated active sites, resulting in numerous oxygen vacancies. With a higher conductivity and distorted crystalline structure, excellent electrochemical NRR activity is realized with a NH3 production rate of 5.19 mmol g–1 h–1 and a Faradaic efficiency of 10.68% at −0.4 V vs reversible hydrogen electrode (RHE). The density functional theory (DFT) calculation demonstrates that introducing oxygen vacancies in thin-layered cobalt oxides could result in an increased density of states (DOS) near the Fermi level, which would accelerate the NRR rate-determining step. Charge transfer could be accelerated through a weak Co 3d–N 2p σ hybrid bond with a lower energy level. No obvious performance decay could be found after six cycles. Furthermore, the sandwiched Co3O4–x/GO catalyst exhibits a low overpotential of 280 mV@10 mA cm–2 and an outstanding durability for the anode OER, even better than those of the benchmark RuO2. Such an inexpensive sandwiched transition metal oxide catalyst shows great potential in the field of overall N2 fixation.