Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co S /Co S /Cu S Nanohybrids.

The rational design of advanced nanohybrids (NHs) with optimized interface electronic environment and rapid reaction kinetics is pivotal to electrocatalytic schedule. Herein, we developed a multiple heterogeneous Co S /Co S /Cu S nanoparticle in which Co S germinates between Co S and Cu S. Using high-angle annular-dark-field imaging and theoretical calculation, it was found that the integration of Co S and Cu S tends to trigger the interface phase transition of Co S , leading to Co S interlayer due to the low formation energy of Co S /Cu S (-7.61 eV) than Co S /Cu S (-5.86 eV). Such phase transition not only lowers the energy barrier of oxygen evolution reaction (OER, from 0.335 eV to 0.297 eV), but also increases charge carrier density (from 7.76×10 to 2.09×10  cm ), and creates more active sites. Compared to Co S and Cu S, the Co S /Co S /Cu S NHs also demonstrate notable photothermal effect that can heat the catalyst locally, offset the endothermic enthalpy change of OER, and promote carrier migrate, reaction intermediates adsorption/deprotonation to improve reaction kinetics. Profiting from these favorable factors, the Co S /Co S /Cu S catalyst only requires an OER overpotential of 181 mV and overall water splitting cell voltage of 1.43 V to driven 10 mA cm under the irradiation of near-infrared light, outperforming those without light irradiation and many reported Co-based catalysts.