Polyethylene glycol induced reconstructing Bi nanoparticle size for stabilized CO2 electroreduction to formate

Abstract

The electrochemical reduction of CO2 (ECR-CO2) to fuels, storing renewable electricity energy from clean energy and recycling CO2 in a carbon neutral and green manner, has been proven to be a feasible strategy for energy storage and conversion. However, the catalysts that drive ECR-CO2 generally suffer from low activity and stability, as well as poor product selectivity. To improve catalyst performance, tuning particle size and morphology has been a key strategy. In this paper, Bi nanoparticle catalysts (Bi30-80) are accurately reconstructed with polyethylene glycol (PEG) using a simple aqueous chemical reduction method. The Bi30-80 catalyst exhibits Faradaic efficiencies as high as 94.7% for ECR-CO2 to produce formate at −0.83 V vs. RHE, and retain their activity for at least 10 h. At more positive potential of −0.78 V vs. RHE, a Faradaic efficiency of 91.3% is reached and the catalysts show no degradation over 20 h of continuous electrolysis. The markedly enhanced activity of a typical Bi30-80 catalyst is due to its appropriate particle size and morphology, assisted by PEG in the catalyst synthesis, which give high electrochemical surface areas and more catalytically active sites. Some visible catalyst deactivation is initially identified, for example, after long-time electrolysis (45 h), caused by a change in morphology and the formation of (BiO)2CO3, confirmed by SEM and XRD. In addition, the effects of HCO3− concentration (or pH) of the electrolyte and the electrode potential impact on catalytic activity and product selectivity of the Bi30-80 catalyst are also studied for performance optimization.