Transitional trimetallic alloy embedded polyacrylamide hydrogel derived nitrogen-doped carbon air-cathode for bioenergy generation in microbial fuel cell

[Display omitted] •FeCoNi alloy nanoparticle embedded in N-doped carbon was synthesized.•The effect of in-situ N-doping and multicomponent doping on ORR activity was examined.•Synergic effect of Fe, Co, Ni nanoparticles, and alloys improved ORR kinetics.•FeCoNi@NC recorded the highest power density of 963.50 mW m−2.•FeCoNi@NC exhibited good COD removal efficiency of 66.84%. Heterometallic carbons are popular materials for application in energy devices due to their high oxygen reduction reaction (ORR) activity and good catalytic stability. Particularly in microbial fuel cells (MFCs), Fe group metal alloys are efficient ORR catalysts. This work has embedded different metallic alloy nanoparticles in polyacrylamide hydrogel derived in-situ nitrogen-doped carbon. All the catalysts (Fe@NC, FeCo@NC, FeNi@NC, and FeCoNi@NC) are used as air cathodes and examined for power generation in single chamber MFCs. Trimetallic composite (FeCoNi@NC) performed better than Pt/C. FeCoNi@NC exhibited superior electrocatalytic activity with an oxygen reduction peak at 0.394 V (vs RHE) and a corresponding peak current density of −0.159 mA. FeCoNi@NC records maximum power output of 963.5 mW m−2 at 2483.2 mA m−2, 3.287 and 1.136 times higher than NC and 10 wt% Pt/C, respectively. This could be due to the uniformly distributed alloy nanoparticles, abundant pyridinic-N, and M−Nx sites that enhance the durability, charge transfer, and power generation in MFCs. These findings suggest that the trimetallic transition metal-carbon (MNC) electrodes could be promising ORR catalysts, justifying their application for energy devices.