Bismuth nanoparticles supported on a high-surface-area nitrogen-doped carbon framework for electrocatalytic CO2 reduction

Bismuth (Bi) based catalysts exhibit high selectivity toward formate in the electrocatalytic reduction of carbon dioxide (CO 2 RR) but are limited by poor intrinsic conductivity and inefficient electron transport. Although three-dimensional (3D) architectures can enhance active surface area and mass/charge transport, conventional binder-assisted fabrication introduces insulating phases and blocks transport pathways, hindering the efficient integration of Bi nanoparticles into conductive frameworks. In this work, Bi nanoparticles with preferentially exposed (012) crystal planes were in situ constructed on three-dimensional porous nitrogen-doped carbon (NC) via a combined hydrothermal and calcination strategy, forming a Bi@NC catalyst for electrocatalytic CO 2 conversion to formate. The optimized Bi@NC-800 catalyst exhibits outstanding CO 2 RR performance, delivering a high Faradaic efficiency of 94 % for formate at -1.0 V vs. RHE, along with a current density of 15 mA·cm -2 . Moreover, the catalyst demonstrates excellent durability, maintaining a stable current density over a 10 h continuous electrolysis test at -1.0 V vs. RHE, while the Faradaic efficiency for formate remains above 90 %. Density functional theory calculations reveal that the electron-rich Bi (012) surface facilitates stable CO 2 adsorption and activation, thereby enhancing the intrinsic catalytic activity. Meanwhile, the nitrogen-doped carbon support significantly improves electrical conductivity and provides additional active sites, enabling efficient charge transfer and accelerated reaction kinetics. Overall, this work presents a rational catalyst design strategy that integrates crystal-facet engineering with conductive carbon supports, offering new insights into the development of high-performance electrocatalysts for selective CO 2 conversion to formate.