Fig. 2: Electrochemical activation and characterizations.

a Schematic illustration of the preparation of electrodes, with steps involving drop−dry cycling and electrochemical activation. b Normalized capacitance (right axis) and contribution proportion of the diffusion process and the surface process (left axis) for GO-B₁₂-GO and GO electrodes. c XRD profiles for analyzing interlayer distance, d_GO-B12-GO, and d_GO. d UV‒vis absorption spectra for quantifying B₁₂ content: the diffused B₁₂ (20-mL electrolyte) and the loosely bound B₁₂ removed from the activated GO-B₁₂-GO electrode by ultrasonication (3-mL water). e B₁₂ content at different electrodes. f CV plots of the GO-B₁₂-GO electrode after activation. g Linear fitting of capacitive current vs. scan rates to estimate the ECSA of different B₁₂-based electrodes. The current densities at 0.2 V vs. NHE in the non-Faradaic region were used for j_a–j_c.