Shape-controlled bismuth nanoflakes as highly selective catalysts for electrochemical carbon dioxide reduction to formate

Nanostructured bismuth (Bi) nanoflakes were designed and directly grown on Cu substrate using a novel pulse electrodeposition method. Compared with conventional bismuth film grown by direct current electrodeposition, Bi nanoflakes have large number of edge and corner sites. As it has been proven by numerical simulation, sharp edge or corner sites of the nanostructures form strong local electric fields, which boost the catalytic activity for the electrochemical reduction of CO2 in aqueous solution. The Bi nanoflakes showed a high HCOO- faradaic efficiency (FE = 79.5%) at low potential of -0.4 V-RHE and achieved a maximum FE close to 100% at -0.6 V-RHE, meaning that the shape control of Bi electrocatalyst is indeed an efficient way to reduce the electrical power consumption for HCOO- production. Moreover, Bi nanoflakes were stable during 10 h operation in 0.1 M KHCO3 aqueous solution. The results suggest that tailoring the nanostructure is a key in developing a high performance noble-metal-free electrocatalyst for electrochemical CO2 reduction in aqueous solution.