Enhanced Electrocatalytic Water Oxidation by Interfacial Phase Transition and Photothermal Effect in Multiply Heterostructured Co<sub>9</sub>S<sub>8</sub>/Co<sub>3</sub>S<sub>4</sub>/Cu<sub>2</sub>S Nanohybrids
Yanan Chang, Zhangyu Ma, Xuyun Lu, S. C. Wang, Jianchun Bao, Ying Liu, Chao Ma
Abstract
Abstract 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 9 S 8 /Co 3 S 4 /Cu 2 S nanoparticle in which Co 3 S 4 germinates between Co 9 S 8 and Cu 2 S. Using high‐angle annular‐dark‐field imaging and theoretical calculation, it was found that the integration of Co 9 S 8 and Cu 2 S tends to trigger the interface phase transition of Co 9 S 8 , leading to Co 3 S 4 interlayer due to the low formation energy of Co 3 S 4 /Cu 2 S (−7.61 eV) than Co 9 S 8 /Cu 2 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 14 to 2.09×10 15 cm −3 ), and creates more active sites. Compared to Co 9 S 8 and Cu 2 S, the Co 9 S 8 /Co 3 S 4 /Cu 2 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 9 S 8 /Co 3 S 4 /Cu 2 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 −2 under the irradiation of near‐infrared light, outperforming those without light irradiation and many reported Co‐based catalysts.