Magnetic field effects on electrochemical CO2 reduction at bismuth based electrocatalyst

Abstract

The application of magnetic fields has garnered significant attention for enhancing the efficiency of electrocatalytic CO₂ reduction (CO₂RR), as it can improve electrocatalytic activity by augmenting mass transport, electron transport, and spin selectivity effects. This study investigates the distinct effects of a magnetic field on two non-magnetic electrocatalysts, bismuth-based metal-organic frameworks (Bi-MOF) and bismuth-based single-atom catalysts (Bi-SACs), to elucidate the mechanisms underlying their promotion of CO₂RR for formate and CO production, respectively. When an external magnetic field of 0.9 T was applied, the Bi-MOF electrode showed a magnetic current gain of 63.2 %, with the Faradaic efficiency for formate increasing to 98.3 % at −1.2 V (vs. RHE). In contrast, the Bi-SACs electrode only achieved a magnetic current gain of 6.2%, with a Faradaic efficiency for CO of 82.4 % at −0.7 V (vs. RHE). Further in-situ spectroscopic experiments and microelectrode tests reveal that the differential magnetic field enhancement observed for the Bi-MOF and Bi-SACs electrodes arises from the spin-selective effect on radical pairs of CO₂ with different adsorption states. These findings provide critical insights into the role of magnetic fields in modulating CO₂RR pathways and highlight the potential for optimizing electrocatalytic performance through spin-selective processes.