Highly Efficient Bismuth-based Catalysts For?Photo?Electrocatalytic Reduction Of CO₂ To Formate

Electrocatalytic and photoelectrocatalytic carbon dioxide reduction technologies represent promising approaches to reduce global warming and energy crisis.Tremendous efforts have been devoted to them,though highly efficient catalytic systems are still under development.In this paper,three novel strategies for CO2 fixation and utilization are proposed from two aspects respectively,including photoelectrocatalysis and electrocatalysis The abstracts for these three works are described as follow:1.In view of the inefficient interface between semiconductor and cocatalyst in most previously reported photoelectrocatalytic systems,we invented a novel one-step Bi3+-assisted chemical etching method,which realized in-situ deposition of metallic bismuth on the surface of Si.Thus-prepared Si/Bi photocathodes exhibit relatively low overpotential,large photocurrent density(?10 mA/cm2 under 0.5 sun)and high formate Faradaic efficiency(up to 90%).In addition,we demonstrated that the photocurrent density can be further enhanced to?12 mA/cm2 by patterning the photocathode using photolithography to expose one third of the Si surface without noticeably compromising the formate selectivity.2.Formic acid(or formate)is suggested to be one of the most economically viable products.However,its commercial viability is limited by both activity and selectivity of electrocatalysts.To address this issue,we utilized defective Bi2O3 nano tubes based catalyst to design an effective electrocatalytic system for CO2 reduction to formate.It enables CO2 reduction to formate with excellent activity,selectivity and long-term working stability.Also,in order to overcome the drawbacks of traditional H-type cells,such as poor mass transfer and limited CO2 solubility,we designed a flow cell with gas diffusion layers.Importantly,its current density reaches?288 mA cm-2 at-0.61 V versus reversible hydrogen electrode within a flow cell reactor under ambient conditions,which substantially exceeds the commercialization requirement.Furthermore,this electrocatalyst is coupled with Si photocathodes and achieves high-performance photoelectrochemical CO2 reduction.3.Based on the above success in electrocatalytic carbon dioxide reduction with flow cells,we creatively developed an Al-CO2 battery using bismuth sulfide-based catalysts.The battery involved metallic Al foil as anode and 1 M KOH as electrolyte.It realized the electrocatalytic carbon dioxide reduction to formate during discharging process(the maximum production rate of formate was up to 35.8 mg cm-2 h-1),and at the same time achieved the conversion of electrical energy to chemical energy.It opened up a new avenue for the development of carbon dioxide fixation and utilization technology,and has also developed a new strategy for energy conversion and storage.