Figure 4. CO 2 RR performances of BiNSs, N-BiNSs, N-BiNSs-1, and N-BiNSs-2: ( a ) Linear sweep Figure 4. CO 2 RR performances of BiNSs, N ‐ BiNSs, N ‐ BiNSs ‐ 1, and N ‐ BiNSs ‐ 2: ( a ) Linear sweep voltammetry curves in 0.5 M KHCO 3 aqueous solutions with saturated gases CO 2 , sweeping speed voltammetry curves in 0.5 M KHCO 3 aqueous solutions with saturated gases CO 2 , sweeping speed of 5 mV s − 1 ; ( b ) the product FE formate at different applied potentials; ( c ) corresponding FE of N- of 5 mV s − 1 ; ( b ) the product FE formate at different applied potentials; ( c ) corresponding FE of N ‐ BiNSs at various potentials; ( d ) the N ‐ BiNSs of j formate recorded at different potentials in 0.5 M BiNSs at various potentials; ( d ) the N-BiNSs of j formate recorded at different potentials in 0.5 M KHCO 3 ; ( e ) the BiNSs and N ‐ BiNSs the relationship between charge current density difference ( △ KHCO 3 ; ( e ) the BiNSs and N-BiNSs the relationship between charge current density difference ( ∆ J) J) and scanning rate; ( f ) stability test of N ‐ BiNSs in the H ‐ type electrolytic cell and Faraday and scanning rate; ( f ) stability test of N-BiNSs in the H-type electrolytic cell and Faraday efficiency efficiency test of formate production. test of formate