CuBi2O4/CuO heterojunction coated with electrodeposited ZnO overlayer for stable solar hydrogen evolution

Abstract

CuBi2O4 has received a lot of attention because of its suitable bandgap and positive onset potential. However, the reported photocurrent density based on the CuBi2O4 photocathode is still far less than its theoretical value. Herein, a layer of amorphous ZnO is coated on the surface of CuBi2O4/CuO heterojunction photocathodes by an electrodeposition method. The photocurrent density achieved by CuBi2O4/CuO/ZnO is 2.1 times that of CuBi2O4/CuO, from 0.56 mA cm−2 to 1.18 mA cm−2 at 0.2 VRHE in 0.5 M Na2SO4. Additionally, after 12 h stability testing, the photocurrent retention rate of CuBi2O4/CuO photocathode with a ZnO protective layer can be maintained at 84%, while only 58% photocurrent retention can be obtained with the bare photocathode. The performance improvement can be attributed to the fact that the electrodeposited amorphous ZnO overlayer provides more active sites, reduces the surface charge transfer resistance, and protects the unstable CuBi2O4/CuO photocathode. This work manifests a ZnO overlayer prepared by the electrodeposition approach is one of efficient strategies to fabricate one durable and high-performance CuBi2O4 based photocathodes.