Engineering High‐Spin State Cobalt Cations in Sulfide Spinel for Enhancing Water Oxidation
Shuowen Bo, Qizheng An, Xiuxiu Zhang, Huijuan Wang, Ju‐Guang Han, Weiren Cheng, Qinghua Liu
Abstract
Abstract The spin states of active sites have a significant impact on the adsorption/desorption ability of the reaction intermediates during the oxygen evolution reaction (OER). Sulfide spinel is not generally considered a highly efficient OER catalyst owing to the low spin state of Co 3+ and the lack of unpaired electrons available for adsorption of reaction intermediates. Herein, it is proposed a novel Nd‐evoked valence electronic adjustment strategy to engineer the spin state of Co ions. The unique f ‐ p ‐ d orbital electronic coupling effect stimulates the rearrangement of Co d orbital electrons and increases the e g electron filling to achieve high‐spin state Co ions, which promotes charge transport by propagating a spin channel and generates a high number of active sites for intermediate adsorption. The optimized CuCo 1.75 Nd 0.25 S 4 catalyst exhibits outstanding electrocatalytic properties with a low overpotential of 320 mV at 500 mA cm −2 and a 48 h stability at 300 mA cm −2 . In situ synchrotron radiation infrared spectra confirm the quick accumulation of key *OOH and *O intermediates. This work deepens the comprehensive understanding of the relationship between OER activity and spin configurations of Co ions and offers a new design strategy for spinel compound catalysts.