Elaborate design of the easy-to-obtain, highly active and corrosion-resistant bifunctional electrocatalysts from earth-abundant elements for water splitting is highly significant for future renewable energy systems. Nickel sulfides have been widely studied in oxygen evolution reaction (OER), because of their excellent stability in alkaline media, however, comparing with the noble metal, the low rate of interfacial reaction and lack of sorptive ability limit the efficiency of water splitting. Herein, for the first time, we developed a one-pot solvothermal reaction for in-situ growth of a pyramid-like Fe-doped Ni3S2 nanostructure on nickel foam (NF) with an excellent bifunctional ability for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction in alkaline media. The obtained electrode, for HER, presents an overpotential of ca. 223 mV at 10 mA cm-2 with a Tafel slope of 51 mV dec-1, and the overpotential of OER needs a ca. 206 mV at 10 mA cm-2 with a Tafel slope of 43 mV dec-1, much better than that of undoped one and other Ni3S2-based electrodes. In combination with experimental results and theoretical calculations, this study demonstrates that, during the process of electrode reaction, the valence state of introduced Fe3+ could be easily changed to +2, which could influence the chemisorption of hydrogen and oxygen-containing intermediates, thus enhancing the overall electrochemical water splitting ability.

Self-adjustable valence states of iron in pyramid-like Ni3S2 bifunctional electrocatalysts for highly enhanced electrochemical overall-water-splitting activity

2019 Spring National Meeting

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