Mo-regulated NiOOH reconstruction and oxygen-intermediate conversion on Co3S4/Ni3S2 heterostructures for overall water splitting

A self-supported Mo-doped Co 3 S 4 /Ni 3 S 2 heterostructure was constructed. • HER and OER overpotentials reach 45.6 and 51.5 mV at 10 mA cm −2 . • Operando Raman reveals earlier formation of a NiOOH-dominated active phase. • Mo suppresses excess OH ⁎ coverage and accelerates oxygen-intermediate turnover. • A symmetric electrolyzer delivers 10 mA cm −2 at a cell voltage of 1.43 V. Dynamic reconstruction of transition-metal sulfides into active oxyhydroxides is critical to the oxygen evolution reaction (OER), yet promoting this transformation at a low anodic potential while avoiding excessive accumulation of oxygenated intermediates remains challenging. Herein, density functional theory (DFT) calculations were used to reveal the electronic effect of Mo incorporation on the Co 3 S 4 /Ni 3 S 2 heterointerface, showing a downward shift of the Ni d -band center and reduced electron localization around adjacent Ni and Co sites. Based on this insight, a self-supported Mo-doped Co 3 S 4 /Ni 3 S 2 heterostructure was synthesized on nickel foam (Mo-Co 3 S 4 /Ni 3 S 2 ). The optimized Mo 0.03 -Co 3 S 4 /Ni 3 S 2 requires overpotentials of only 51.5 mV and 45.6 mV to deliver 10 mA cm −2 for OER and HER. A two-electrode electrolyzer using Mo-Co 3 S 4 /Ni 3 S 2 as both electrodes reaches 10 mA cm −2 at only 1.43 V. Methanol-probe measurements indicate reduced OH ⁎ accumulation after Mo incorporation, while in-situ Raman spectroscopy identifies the reconstructed NiOOH layer as the OER-active phase and reveals its formation at a lower anodic potential. Further calculations show that Mo brings hydrogen adsorption closer to thermoneutral and lowers the thermodynamic limitation of OER by regulating oxygenated-intermediate adsorption. This work provides a general strategy for regulating dynamic catalyst reconstruction and interfacial reaction processes, which may advance the development of efficient electrocatalysts for sustainable hydrogen production. Download: Download high-res image (132KB) Download: Download full-size image