Polymeric carbon nitride supported Bi nanoparticles as highly efficient CO2 reduction electrocatalyst in a wide potential range

It is still a great challenge to develop electrocatalysts for CO2 reduction with high product selectivity and energy conversion efficiency. In this work, Bi nanoparticles supported on polymeric carbon nitride (Bi/CN) have been prepared for CO2 electrocatalytic conversion. Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) analyses confirm the existence of Bi2O3 on Bi particle surface, forming Bi/Bi2O3 nanoparticles. CN, as the support, has been found not only to improve the dispersibility of Bi/Bi2O3 nanoparticles, but also to enhance the CO2 adsorption on Bi/CN surface owing to the existence of amino and cyano groups. The electronic structure of Bi/CN has been optimized by the interaction between CN and Bi: the electron transfer from Bi to CN results in electron-deficient Bi sites which stabilize CO2-, HCOO- intermediates and accelerate the formation rate of HCOOH. As a result, the maximum Faradaic efficiency of HCOOH reaches 98% at -1.3 to -1.5 V versus reversible hydrogen electrode (vs. RHE) and remains over 91% in a wide potential window of about 500 mV (-1.1 ∼ -1.6 V vs. RHE). The as-obtained Bi/CN in this work shows superior performance to most of the previously reported Bi-based electrocatalysts.