Sunlight-promoted CO2 electroreduction with staggered p-n heterojunction by indium-doped bismuth 3D nanoflower structure on oxidized copper foam as self-standing photoelectric cathode over a wide potential window

Exploiting suitable photocathodes to achieve high photocurrent and long-term endurance is still a great challenge in photoelectrocatalytic CO reduction (PEC CO) reactions. Herein, an In-doped BiO decorated oxidized copper foam (CBIO/CF) self-standing photoelectric cathode is well designed by the self-assembly process without an externally added binder. Via sunlight-promoted strategy, CBIO/CF with a unique 3D hierarchical nanoflower structure displays a superior faradaic efficiency of 90.0 % towards HCOOH over a wide potential window from −0.87 ∼ −1.17 V and reaches 97.8 % at −0.87 V with a partial current density of 14.41 mA cm. The in-situ Fourier transform infrared spectroscopy (FTIR) analysis demonstrates the abundant oxygen defects induced by In doping boost CBIO/CF absorbing substantive intermediate species related with formate generations, and porous structure accelerating mass transportation. Moreover, the well-designed staggered p-n heterojunctions of CuO and In-doped BiO on the surface of catalysts favor the generation and separation of electron/hole pairs and contribute to the photocatalytic reduction of CO under a bias voltage. This work paves the way for rational regulation of self-supporting photoelectrode for PEC CO to HCOOH with suitable conduction band valence bands and high performance and stability.