NiCoOx@NiCo core-shell nanoparticles supported on Ti3C2Tx as cathode electrocatalysts for microbial fuel cells

Abstract

The intrinsically sluggish oxygen reduction reaction (ORR) at platinum-group-metal-free cathodes remains a key bottleneck for the practical deployment of microbial fuel cells (MFCs). Ti₃C₂T_x MXene is a promising conductive scaffold, yet its ORR activity is hindered by strong O₂ adsorption at Ti sites, leading to sluggish kinetics at neutral pH. Here, we address this limitation by developing a targeted chemical-reduction strategy that assembles NiCo alloy nanocores encapsulated in a thin NiCo-oxide shell (~4 nm) onto Ti₃C₂T_x, forming a (NiCoO_x@NiCo)/Ti₃C₂T_x heterostructure catalyst. The core-shell domains modulate the local electronic environment, lower the O₂ binding energy, and introduce abundant active sites, thereby leveraging the high conductivity of Ti₃C₂T_x. As an air-cathode MFC treating glucose-supplemented wastewater, the catalyst delivers a current density of 4.5 A m^-2 and a peak power density of 1.6 W m^-2, outperforming pristine Ti₃C₂T_x. This work establishes a generalizable heterostructure design strategy for activating MXene-based catalysts toward efficient neutral-pH ORR, bridging fundamental catalyst design with practical microbial fuel cell applications.