Structurally and electronically coupled Bi/Bi3Ni–carbon dot catalyst for efficient and long-lived CO2 electroreduction to formate

Abstract

The development of efficient and durable electrocatalysts for CO2 electroreduction remains a critical challenge to sustainable fuel generation. Herein, we report a structurally and electronically engineered Bi–based catalyst comprising a Bi/Bi3Ni heterostructure embedded with nitrogen-doped carbon dots (N − CDs), synthesized via a chelation-assisted porous nanostructuring method. The incorporation of Ni enhances electronic conductivity and suppresses Bi oxidation, while the N − CDs modulate the local Fermi level and p-orbital electron density, stabilizing OCHO* intermediates and improving CO2 activation. Operando X-ray absorption spectroscopy and in-situ Raman analyses reveal that BiNi–N-CDs undergo Bi3 + →Bi0 reduction and form bidentate formate intermediates, while Ni alloying and N-CDs synergistically lower the OCO → OCHO hydrogenation barrier, enabling efficient formate production at mild potentials, supported by density functional theory calculations. The optimized BiNi (10 %)–0.6 mL N − CDs catalyst achieves a maximum formate Faradaic efficiency of 96 % at −0.9 V vs. RHE, while exhibiting outstanding operational stability over 100 h, with minimal performance loss. This work demonstrates a synergistic strategy that combines alloy engineering, electronic modulation, and interfacial design to realize highly selective and long-lived CO2 reduction catalysts.