Spinel Nickel–Cobalt Oxide Nanorods Supported on Ti₃C₂T_x-MXene Nanosheets as Electrocatalysts for the Methanol Oxidation Reaction via a CO-Free Pathway

Abstract

In this work, we demonstrated the conceptual design and controlled fabrication of a 1D/2D heterojunction composed of NiCo 2 O 4 nanorods grown on Ti 3 C 2 T x -MXene nanosheets. The developed NiCo 2 O 4 /Ti 3 C 2 T x -MXene enables a stable hybrid structure, which results in a remarkable methanol oxidation reaction (MOR) via a CO-free pathway. It exhibits higher mass and specific activity and a longer operating life (30,000 s) compared to conventional Pt/C. The enhanced MOR kinetics of the NiCo 2 O 4 /Ti 3 C 2 T x -MXene catalyst can be attributed to the substantial electronic exchanges between the NiCo 2 O 4 nanorods and MXene, along with a concurrent downshift of the d-band center. Electrochemical studies based on in situ FTIR spectroscopy experiments reveal that NiCo 2 O 4 /Ti 3 C 2 T x -MXene exhibits superior CH 3 OH and OH* adsorption, facilitating the creation of H 2 CHOO* intermediates. When utilized as the anode catalyst in an alkaline direct methanol fuel cell (ADMFC), the NiCo 2 O 4 / Ti 3 C 2 T x -MXene electrocatalyst outperforms traditional Pt/C, demonstrating an outstanding power density of 52 mW/cm 2 during practical ADMFC operation.