Bismuth Anchored on MWCNTs with Controlled Ultrafine Nanosize Enables High-Efficient Electrochemical Reduction of Carbon Dioxide to Formate Fuel

Abstract

Metal nanoparticles usually exhibit unique catalytic performance, while unfortunately, so far, the Bi nanoparticles (NPs) (<5 nm) have not been employed for the electrochemical reduction of carbon dioxide (ECR-CO2). Here, we report a facile and mild strategy to fabricate Bi nanocrystals in situ decorated on functionalized multiwalled carbon nanotubes (Bi NP@MWCNTs) as a high-performance catalyst for ECR-CO2. The transmission electron microscopy (TEM) images revealed that the Bi NPs with an average particle size of 4.4 nm were uniformly supported on the MWCNTs. The resulting Bi NP@MWCNTs exhibit much higher electrocatalytic activity, Faradaic efficiency (FE), and current density than the Biblank catalyst toward CO2 reduction to formate. At −1.5 V versus SCE (saturated calomel reference electrode), the maximum FE of 95.2% for formate was achieved on a Bi NP@MWCNT catalyst with a current density of 10.7 mA cm−2. MWCNTs play an important role in the markedly enhanced activity for CO2 reduction to formate on Bi NP@MWCNT catalysts. Besides, the formation of the *OCOH intermediate is considered as the rate-limiting step for CO2 conversion to formate on Bi NP@MWCNT catalysts. The results indicate that the as-prepared Bi NP@MWCNT catalysts exhibit promising potential in the electrochemical reduction of CO2 to fuels.