Abstract:
Hydrogen plays a key role in deep decarbonization for realization of net-zero carbon dioxide emission by 2050. Presently, the most popular and economical commercial process for H2 production is steam–methane reforming, which uses fossil fuels as the raw material and produces comparable amounts of CO2 as the by–product. It is definitely an environmental unfriendly and a non–sustainable H2 production process, and development of green H2 production is in urgent need. In this regard, renewable energy driven electrolytic water splitting has been gaining rapidly increasing popularity and is considered by many the most promising green H2 production process for future hydrogen economy infrastructure. It is also considered a necessary energy storage approach to resolve the detrimental unreliability and intermittency issues of renewable energies. The high cost of electricity however severely limits the prevailing of this technology, and cost–effective highly efficient and stable electrocatalysts, aiming to reduce the necessary working potential for cost competitiveness, are critically important for the prevailing of the technology. For catalyst development, quantity and quality of the active sites of the catalysts are the two key aspects, which can be improved through nanostructuring and composition engineering, respectively. Furthermore, the identification and mechanistic understanding of the active sites of the catalysts are fundamental and X-ray absorption spectroscopy is a powerful tool for the purposes. Here, two recent examples from our lab are presented to illustrate the approch, one concerning effects of Au nanocrystal decoration on oxygen evolution reaction (OER) performances of a FeCoNi-MOF [1] and the other on the hydrogen evolution reaction (HER) performances of a (NixFeyCo6-x-y)Mo6C catalyst [2]. It is found that Au nanocrystal decoration enhances the OER performance of the FeCoNi-MOF through raising the oxidation states of the three metallic centers, Fe, Co, and Ni, of the FeCoNi-MOF. It is further found that the activities of the three metallic centers toward catalyzation of the OER runs in the order Ni > Co > Fe. As for (NixFeyCo6-x-y)Mo6C, it catalyzes the HER through the Volmer-Heyrovsky route.
Keywords – X-Ray Absorption Spectroscopy, Electrolytic Water Splitting, Hydrogen Evolution Reaction, Oxygen Evolution Reaction, Electrocatalyst.
References:
- -C. Cheng, P.-Y. Cheng, C.-L. Huang, D. Senthil Raja, Y.-J. Wu, and S.-Y. Lu, “Gold nanocrystal decorated trimetallic metal organic frameworks as high performance electrocatalysts for oxygen evolution reaction,” Appl. Catal. B. – Environ., 286, 119916, 2021.
- -G. He, P.-Y. Cheng, C.-C. Cheng, C.-L. Huang, C.-T. Hsieh, and S.-Y. Lu, “(NixFeyCo6-x-y)Mo6C Cuboids as Outstanding Bifunctional Electrocatalysts for Overall Water Splitting,” Appl. Catal. B. – Environ., 290, 120049, 2021.