A Bismuth Species-Decorated ZnO/p-Si Photocathode for High Selectivity of Formate in CO2 Photoelectrochemical Reduction

Photoelectrochemical (PEC) reduction of CO2 to high value-added chemicals or fuel is an effective way to remit insufficient energy supply and global warming. Herein, Bi speciesmodified p-n heterojunction ZnO/p-Si was synthesized by a hydrothermal method and a subsequent electrodeposition process. For the PEC CO2 reduction reaction (CO2RR), the obtained photocathode Bi-Bi2O3/ZnO/p-Si not only improves the light absorption capacity because of p-Si and plasma metal Bi, but also increases the selectivity of CO2 reduction products because of the existence of Bi species. In particular, compared with the electrochemical CO2RR, the faraday efficiency of formate shows a 1.8 fold increase for the optimal sample Bi-Bi2O3/ZnO/ p-Si reaching 84.3% in the PEC CO2RR at -0.95 V vs RHE. More importantly, the current density and product selectivity have no decay within 8 h, implying its high stability. In addition,, a high applied bias photon-to-current efficiency of 1.14% and an energy efficiency value of 56.21% were achieved for the Bi-Bi2O3/ZnO/p-Si photocathode at -0.95 V vs RHE, confirming its high PEC activity. A possible electron transfer mechanism for the Bi-Bi2O3/ZnO/p-Si photocathode is also proposed.

Automated summary

The study confirmed the high performance of the Bi-Bi2O3/ZnO/p-Si photocathode in the CO2 reduction reaction through a series of experiments, which not only improved the light absorption capacity, but also increased the selectivity of CO2 reduction products. Furthermore, this material showed high stability and photoelectrochemical activity.