Optimization of oxygen evolution activity by tuning e _g band broadening in nickel oxyhydroxide

摘要

Nickel oxyhydroxides (NiOOH) derived from the reconstruction of Ni-based pre-catalysts are activespecies for the oxygen evolution reaction (OER). Although chemically similar, these NiOOH exhibitdifferentiated OER activities that show strong correlations to their synthetic origins. To unearththe mechanism behind this, three NiOOH were prepared by subjecting NiS_2, NiSe_2 and Ni_5P_4 tochronopotentiometry treatment. We found that a stronger strain leads to a greater NiO6 octahedrondistortion in NiOOH, which results in the broadening of the e_g band (3d electron states with e_gsymmetry) to a great extent. The increase in e_g band broadening can facilitate electron transfer from theelectrocatalysts to the external circuit, which ultimately enhances the catalytic performance. Wedemonstrated the universality of this concept by extending it to a NiFe oxyhydroxide system. This studyshows the first evidence of the relationship between structure and catalytic performance by revealingthe role of e_g band broadening, paving the way toward designing efficient OER electrocatalysts.