Ultrathin, Porous and Oxygen Vacancies-Enriched Ag/WO3-x Heterostructures for Electrocatalytic Hydrogen Evolution.

Exploring advanced electrocatalysts for electrocatalytic hydrogen evolution is highly desired but remains a challenge due to the lack of an efficient preparation method and reasonable structural design. Herein, we deliberately designed novel Ag/WO3-x heterostructures through a supercritical CO2 -assisted exfoliation-oxidation route and the subsequent loading of Ag nanoparticles. The ultrathin and oxygen vacancies-enriched WO3-x nanosheets are ideal substrates for loading Ag nanoparticles, which can largely increase the active site density and improve electron transport. Besides, the resultant WO3-x nanosheets with porous structure can form during the electrochemical cycling process induced by an electric field. As a result, the exquisite Ag/WO3-x heterostructures show an enhanced hydrogen evolution reaction (HER) activity with a low onset overpotential of ≈30 mV, a small Tafel slope of ≈40 mV dec-1 at 10 mA cm-2 , and as well as long-term durability. This work sheds light on material design and preparation, and even opens up an avenue for the development of high-efficiency electrocatalysts.