The Regulation Effect of Residual S in the Reconstructed Layer of Transition Metal Sulfides on Catalytic Performance and Synergistic Enhancement Mechanism For Water Oxidation

Transition metal chalcogenides (TMCs) are recognized as OER pre-catalysts, and their high-valence transition metal (oxy)hydroxides derived from electrochemical reconstruction are the active species in the water oxidation. However, the regulating effect and existence form of the residual chalcogen in the reconstructed layer haven’t been unraveled in detail, moreover, the catalytic mechanism remains unclear. This work, taking Cu1-xCoxS as an example, studies the existential state of residual S in the reconstructive layer after sulfides dissolution, and explores the effect of residual S on active intermediates through synchrochromic radiation, in-situ Raman and isotope labeling experiments. The results manifest that the residual S is doped into the reconstructive layer to form CuCo-hydroxysulfides, which evokes the LOM mechanism by activating the reactivity of lattice oxygen. Meanwhile, the residual S also regulates the electronic structure and coordination environment of metal sites, thus ameliorating the adsorption/desorption kinetics of oxygen-containing intermediates in AEM. Therefore, a synergistic enhancement mechanism of both AEM and LOM is proposed, combining with DFT calculation. As scheduled, Cu0.4Co0.6S-derived Cu0.4Co0.6OSH owns the excellent OER activity and satisfying stability. The outcomes are of guiding significance for understanding the relationship between surface composition/structure and reactivity toward water oxidation of TMCs.