Gadolinium‐Enhanced Bismuth Cathode for High‐Performance CO ₂ ‐to‐Formate Conversion Across Electrochemical and Bioelectrochemical Energy Systems

Electrocatalytic CO₂ conversion to formate represents a crucial pathway for carbon cycling and renewable energy storage, yet catalysts exhibiting high activity, selectivity, and stability remain elusive. This study employs a rare-earth-regulated strategy to construct a carbon-encapsulated gadolinium-doped bismuth catalyst (Gd-Bi@C) via a one-step hydrothermal process. In a flow cell, this catalyst achieved a formate Faradaic efficiency of 95.58% at -1.1 V versus RHE and operated stably for over 170 h at current densities exceeding 400 mA cm⁻². In situ characterization confirmed that gadolinium doping optimized the electronic structure of bismuth, promoting the formation of the *OCHO intermediate while suppressing hydrogen evolution. Furthermore, Gd-Bi@C demonstrates exceptional cross-system applicability: achieving a peak power density of 2.166 mW cm⁻² in a Zn-CO₂ battery and sustaining a current density of 12.40 ± 2.20 A m⁻² in a microbial electrolysis coupled CO₂ reduction system (MEC-CO₂). This work bridges electrochemical and bioelectrochemical CO₂ conversion systems using a single rare-earth-modified catalyst, providing an integrated material platform for multi-scenario carbon utilization and energy storage.