The fabrication of silane modified graphene oxide supported Ni–Co bimetallic electrocatalysts: A catalytic system for superior oxygen reduction in microbial fuel cells

Microbial fuel cells (MFCs) exploit the ability of microorganisms to generate clean energy from organic pollutants in wastewater. However, the poor cathode performance and the use of the expensive rare metal platinum as a catalyst limit their application and scalability. In this study, we have synthesised a Ni–Co/GO nanocomposite and applied it as a potential cathode catalyst to single-chamber MFCs. To improve the performance of a Ni–Co-based hybrid nanocomposite, the support of graphene oxide (GO) is covalently modified with γ-amino propyl tri-ethoxy silane (APTES) through a silane modification reaction. The physical and chemical properties of the synthesised materials are characterised with Fourier transform infrared (FTIR), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) techniques. A microscopic study has shown that metal nanoparticles are distributed uniformly on the MGO matrix. The electrocatalytic activity of the synthesised hybrid nanocatalysts is analysed for oxygen reduction reaction (ORR). A cyclic voltammetry experiment has shown that the Ni–Co/MGO catalyst exhibits a higher reduction peak current value and a higher positive onset potential than the Ni–Co/GO catalyst and Pt/C catalyst, indicating an enhanced ORR activity of the Ni–Co/MGO catalyst. Ni–Co/MGO also exhibits the highest initial current of 0.116 mA in the chronoamperometry test, which decreases to 0.049 mA after 16000 s. The electrochemical results demonstrate that the synthesised Ni–Co/MGO catalyst has a higher electrocatalytic activity and higher stability than the state-of-the-art Pt/C catalyst. More importantly, a MFC with Ni–Co/MGO as a cathode catalyst shows the maximum power density of 1003.18 mWm⁻², which is much higher than in the case of the Ni–Co/GO catalyst (889.6 mWm⁻²) and approximately 2.1 times higher than that of the state-of-the-art Pt/C (483.48 mWm⁻²). Consequently, the Ni–Co/MGO nanocomposite also shows the highest open circuit voltage of 0.857 V among the other studied catalysts. Moreover, the Ni–Co/MGO catalyst has a lower biofouling level than a commercial 10 wt% Pt/C catalyst, which shows that the synthesised cathode catalyst is superior in terms of stability, overall performance and usage. These results suggest that the newly developed Ni–Co/MGO catalyst can be applied as a potential substitute for the Pt/C cathode catalyst for the practical application of MFCs.