Fig. 3: Mechanism analysis.

a Tafel plots of different samples. b The production rates of formate in 0.5 M KHCO3-H2O (blue column) and 0.5 M KHCO3-D2O (purple column). The columns with shadows represent samples after thermal treatment. c The KIE value of H/D for different samples. The red and black lines represent samples before and after annealing, respectively. d The production rates of formate over BOC-1, BOC-2, BOC-3 and BOC-4 in K2HPO4, K2CO3 and K2SO4 electrolytes. The error bars represent the standard deviation of three independent experiments.