Fig. 4. HER performance of n-Cu/BP catalysts and control samples.

a LSV curves and b Tafel plots of the catalysts in 1 M KOH with a scan rate of 5 mVs⁻¹. c TOFs of Cu, Co, and CuCo atoms on BP at different overpotentials. d Mass activities of the catalysts on the basis of Cu, Co and CuCo atoms. e Overpotentials of Cu/BP and Co/BP with different Cu and Co loading, respectively, and the corresponding TOFs activity trend. f Overpotentials of CuCo/BP with different CuCo ratios (fixed the feeding amount of Cu or Co at 0.05 mmol and change in Co or Cu amount), and the corresponding activity trend. g Nyquist plots of experimental data for BP, CuCo/BP, n-Co/BP, and n-Cu/BP. h Stability of n-Cu/BP and BP catalysts.