Accelerate charge separation in Cu2O/MoO2 photocathode for photoelectrocatalytic hydrogen evolution.

Cu 2 O/MoO 2 hybrid was prepared for photoelectrocatalytic water reduction. Theoretical and experimental results both indicate the charge transfers from Cu 2 O to MoO 2 and forms an intimated binding interface via ionic interaction. A well-aligned energy level was formed between Cu 2 O and MoO 2 , which enables the formation of an internal electric field at their interfaces, facilitating charge separation, directional transfer, and reaction. The reduction of Cu+ and the photocorrosion of Cu 2 O were inhibited via the deposited MoO 2 , and finally, Cu 2 O/MoO 2 hybrid exhibited improved PEC activity and stability. [Display omitted] • Cu 2 O was chemically bonded with MoO 2 and formed a compact hybrid structure as well as exhibited good structural stability. • Cu 2 O/MoO 2 photocathode delivers 6.85 times higher photocurrent density than that of Cu 2 O and excellent operating stability. • Cu 2 O and MoO 2 construct an energetically favorable energy band bending that inhibits the photogenerated charge reflux and recombination. • Metallic MoO 2 can stabilize the Cu 2 O surface against the reduction of Cu+ via a formed internal electric field, thus suppressing photocorrosion. Photoelectrocatalyzing water reduction is a potential approach to building a green and sustainable society. As a benchmark photocathode, Cu 2 O receives much attention but faces serious charge recombination and photocorrosion. This work prepared an excellent Cu 2 O/MoO 2 photocathode via in situ electrodeposition. A systematical study of theory and experiment demonstrates that MoO 2 not only effectively passivates the surface state of Cu 2 O as well as accelerates reaction kinetics as a cocatalyst, but also promotes the directional migration and separation of photogenerated charge. As expected, the constructed photocathode exhibits a highly enhanced photocurrent density and an appealing energy transformation efficacy. Importantly, MoO 2 can inhibit the reduction of Cu+ in Cu 2 O via a formed internal electric field and shows excellent photoelectrochemical stability. These findings pave the way to designing a high-activity photocathode with high stability. [ABSTRACT FROM AUTHOR]