Key role of eg* band broadening in nickel-based oxyhydroxides on coupled oxygen evolution mechanism
Haoyin Zhong, Qi Zhang, Junchen Yu, Xin Zhang, Chao Wu, Hang An, Yifan Ma, Hao Wang, Jun Zhang, Yong‐Wei Zhang, Caozheng Diao, Zhi Gen Yu, Shibo Xi, Xiaopeng Wang, Junmin Xue
Abstract
Abstract A coupled oxygen evolution mechanism (COM) during oxygen evolution reaction (OER) has been reported in nickel oxyhydroxides (NiOOH)-based materials by realizing e g * band (3 d electron states with e g symmetry) broadening and light irradiation. However, the link between the e g * band broadening extent and COM-based OER activities remains unclear. Here, Ni 1-x Fe x OOH (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 e g * band broadening could facilitate the * OH deprotonation. Meanwhile, in high potential region where the photon utilization is the rate-determining step, a stronger e g * band broadening would widen the non-overlapping region between d z 2 and a 1g * orbitals, thereby enhancing photon utilization efficiency. Consequently, a stronger e g * 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 = NiS 2 , NiSe 2 , Ni 4 P 5 ) with varying extent of e g * band broadening. Such an understanding of the COM would provide valuable guidance for the future development of highly efficient OER electrocatalysts.