Bismuth-Oxide-Decorated Graphene Oxide Hybrids for Catalytic and Electrocatalytic Reduction of CO2.

Abstract

Global warming challenges are fueling the demand to develop an efficient catalytic system for the reduction of CO2 , which would contribute significantly to the control of climate change. Herein, as-synthesized bismuthoxide-decorated graphene oxide (Bi2 O3 @GO) was used as an electro/thermal catalyst for CO2 reduction. Bi2 O3 @GO is found to be distributed uniformly, as confirmed by scanning electron and transmission electron microscopic analysis. The X-ray diffraction (XRD) pattern shows that the Bi2 O3 has a β-phase with 23.4 m2 g-1 BET surface area. Significantly, the D and G bands from Raman spectroscopic analysis and their intensity ratio (ID /IG ) reveal the increment in defective sites on GO after surface decoration. X-ray photoelectron spectroscopic (XPS) analysis shows clear signals for Bi, C, and O, along with their oxidation states. An ultra-low onset potential (-0.534 V vs. RHE) for the reduction of CO2 on Bi2 O3 @GO is achieved. Furthermore, potential-dependent (-0.534, -0.734, and -0.934 vs. RHE) bulk electrolysis of CO2 to formate provides Faradaic efficiencies (FE) of approximately 39.72, 61.48, and 83.00 %, respectively. Additionally, in time-dependent electrolysis at a potential of -0.934 versus RHE for 3 and 5 h, the observed FEs are around 84.20 % and 87.17 % respectively. This catalyst is also used for the thermal reduction of CO2 to formate. It is shown that the thermal reduction provides a path for industrial applications, as this catalyst converts a large amount of CO2 to formate (10 mm).