γ-Fe2O3 decorating N,S co-doped carbon nanosheets as a cathode electrocatalyst for different-scenario fuel cells

Abstract

Rechargeable Zn-air batteries (RZABs) and microbial fuel cells (MFCs) are gaining significant attention as highly promising energy storage technologies due to their compelling cost-effectiveness, extraordinary energy density, environmentally friendly nature, and an exceptional safety profile. Designing a cost-effective, highly efficient, and long-lasting bifunctional electrocatalyst for both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) is a remarkable yet challenging endeavor. Transition metal oxide (TMO)-based electrocatalysts are poised to emerge as formidable contenders to well-established noble metal catalysts. In our research, we have developed a concise and refined method to fabricate a carbon-based material doped with N and S and infused with γ-Fe₂O₃. This design has yielded the γ-Fe₂O₃@SNC-800 catalyst, exhibiting exceptional catalytic performance comparable to Pt/C and RuO₂, especially with an ORR half-wave potential (E_1/2) of 0.849 V vs. RHE and an OER onset potential of 1.57 V at a current density of 10 mA cm⁻² in alkaline environments. One particularly noteworthy observation is the use of γ-Fe₂O₃@SNCs-800 as the cathode catalyst in RZABs, where it demonstrates a remarkable peak power density of 214.3 mW cm⁻² and impressive charge–discharge cycling stability lasting up to 133 h. Additionally, this catalyst material exhibits superior energy density and sustains extended continuous operation when integrated into the cathode of MFCs. Finally, the utilization of density functional theory (DFT) calculations provides compelling theoretical support, enabling a profound understanding of the electrocatalytic performance mechanism during the ORR. Our results suggest a straightforward approach for developing efficient bifunctional electrocatalysts for different-scenario fuel cells.