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Research Reveals the Significance of Non-Metal Element in CuCo Spinel Structure Catalysts

Oxygen evolution reaction (OER), as a vital half-reaction in some clean energy storage and conversion technologies including rechargeable metal-air batteries, regenerative fuel cells and electrochemical water splitting, has been of crucial importance for exploring highly efficient sustainable energy to substitute exhaustible fossil fuels.

Among them, electrochemical water splitting can effectively produce clean and reproducible hydrogen fuels through renewable energy sources as power input like solar energy, etc. Unfortunately, the efficiency of water splitting is mainly impeded by the high anodic overpotential of OER, in which seeking efficient and stable electrocatalysts is highly desirable.

It has been considered that spinel-structure materials can be meaningful alternative catalysts for OER. In recent years, many works are devoted to developing CuCo spinels for OER catalysis based on the synergistic effect regarding bimetals in spinel, morphology characteristic and conductive substrates, while the mechanism, especially the function of non-metallic in the structure, has not been systematically studied, as well as the influence on the electronic structure of metal active centers and improved performance.

Very recently, through a facile hydrothermal method with or without the oxidation of ammonia water, Prof. Xiaohong Yan, Dr. Dewei Rao and colleagues in Jiangsu University elaborately fabricated oxy-spinel Cu1-xCo2+xO4 nanoflakes and thio-spinel Cu1-xCo2+xS4 nanospheres.

The as-prepared Cu1-xCo2+xO4 has a low overpotential of only 267 mV for achieving the current density of 10 mA/cm2, outperforming Cu1-xCo2+xS4 (297 mV), and their activities are superior to the commercial precious catalyst of RuO2 (321 mV). X-ray photoelectron spectroscopy analysis exhibits the higher ratio value of Co(III)/Co(II) in Cu1-xCo2+xO4 than that in Cu1-xCo2+xS4, suggesting that the strongly-electronegative oxygen efficiently predominates in regulating valence states of Co active sites in spinel structures.

Remarkably, density functional theory simulation further reveals that the increased valence state of Co could accelerate the electron exchange between catalysts and oxygen adsorbates during electrocatalysis, thus contributing to the higher OER activity of Cu1-xCo2+xO4 catalysts.

Our work provides the systematic exploration of OER catalytic mechanism on the non-metallic electronic regulation in CuCo oxy-/thio-spinel for water oxidation, which will guide the further design of high-performance materials for new spinel structure catalysts.

See the article: Yang H, Gao S, Rao DW, Zhang CN, Zhou XC, Yang SK, Ye JJ, Yang SS, Lai FL, Yan XH. Non-metallic electronic regulation in CuCo oxy-/thio-spinel as advanced oxygen evolution electrocatalysts. Sci. China Chem., 2020, DOI: 10.1007/s11426-020-9895-2.


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