Concentration-dependent effects of nickel doping on activated carbon biocathodes

This study aims to investigate the effect of nickel electrocatalyst addition on an activated carbon (AC) biocathode. Three types of electrodes were tested with abiotic and biological electrochemical experiments: Control AC electrodes without nickel; AC electrodes with 0.01% wt. metal loading; and AC electrodes with 5% wt. metal loading. High metal loading resulted in measurable improvement of electrocatalytic H2 production, compared to the other 2 electrodes, which achieved a similar electron recovery to H2. Higher acetate production was achieved with increasing metal loading. Microbial growth in the electrolyte and on the electrode was influenced by the addition of nickel at both loadings, but the effect was not concentration-dependent. Each electrode resulted in unique microbial community composition in the electrolyte. Evidently, nickel can affect the biocathode performance due to both catalytic and non-catalytic effects.