Figure 5. ( a ) The LSV curve in a flow cell under CO 2 atmosphere; ( b ) Stability test of the material Figure 5. ( a ) The LSV curve in a flow cell under CO 2 atmosphere; ( b ) Stability test of the material at − 1.2 V vs. RHE and corresponding Faraday efficiency test of formate production of N ‐ BiNSs; ( c ) at − 1.2 V vs. RHE and corresponding Faraday efficiency test of formate production of N-BiNSs; Polarization curve of N ‐ BiNSs||IrO 2 couple in the two ‐ electrode system; ( d ) Chronoamperometry ( c ) Polarization curve of N-BiNSs||IrO 2 couple in the two-electrode system; ( d ) Chronoamperometry measurement of N ‐ BiNSs||IrO 2 couple at 3 V. measurement of N-BiNSs||IrO 2 couple at 3