P and Se Binary Vacancies and Heterostructures Modulated MoP/MoSe Electrocatalysts for Improving Hydrogen Evolution and Coupling Electricity Generation.

It is not enough to develop an ideal hydrogen evolution reaction (HER) electrocatalysts by single strategy. Here, the HER performances are significantly improved by the combined strategies of P and Se binary vacancies and heterostructure engineering, which is rarely explored and remain unclear. As a result, the overpotentials of MoP/MoSe -H heterostructures rich in P and Se binary vacancies are 47 and 110 mV at 10 mA cm in 1 m KOH and 0.5 m H SO electrolytes, respectively. Especially, in 1 m KOH, the overpotential of MoP/MoSe -H is very close to commercial Pt/C at the beginning and even better than Pt/C when current density is over 70 mA cm . The strong interactions between MoSe and MoP facilitate electrons transfer from P to Se. Thus, MoP/MoSe -H possesses more electrochemically active sites and faster charge transfer capability, which are all in favor of high HER activities. Additionally, Zn-H O battery with MoP/MoSe -H as cathode is fabricated for simultaneous generation of hydrogen and electricity, which displays the maximum power density of up to 28.1 mW cm and stable discharging performance for 125 h. Overall, this work validates a vigorous strategy and provides guidance for the development of efficient HER electrocatalysts.