A coupled oxygen evolution mechanism (COM) during oxygen evolution reaction (OER) has been reported in nickel oxyhydroxides (NiOOH)-based materials by realizing eg* band (3d electron states with eg symmetry) broadening and light irradiation. However, the link between the eg* band broadening extent and COM-based OER activities remains unclear. Here, Ni1-xFexOOH (x = 0, 0.05, 0,2) are prepared to investigate the underlying mechanism governing COM-based activities. It is revealed that in low potential region, realizing stronger eg* band broadening could facilitate the *OH deprotonation. Meanwhile, in high potential region where the photon utilization is the rate-determining step, a stronger eg* band broadening would widen the non-overlapping region between dz2 and a1g* orbitals, thereby enhancing photon utilization efficiency. Consequently, a stronger eg* band broadening could effectuate more efficient OER activities. Moreover, we demonstrate the universality of this concept by extending it to reconstruction-derived X-NiOOH (X = NiS2, NiSe2, Ni4P5) with varying extent of eg* band broadening. Such an understanding of the COM would provide valuable guidance for the future development of highly efficient OER electrocatalysts.
Coupled oxygen evolution mechanism provides an optimized electron transfer route during oxygen evolution process, but the underlying structure-activity relationship is still unclear. Here the authors investigate the role of eg* band broadening on the coupled oxygen evolution mechanism-based activities for Fe-doped NiOOH materials.