Spinel Nickel–Cobalt Oxide Nanorods Supported on Ti<sub>3</sub>C<sub>2</sub>T<sub><i>x</i></sub>-MXene Nanosheets as Electrocatalysts for the Methanol Oxidation Reaction via a CO-Free Pathway
Naresh Narayanan, Huiyuan Liu, Weiqi Zhang, Balamurali Ravichandran, Qian Xu, Lindiwe Khotseng, Yi Cheng, Huaneng Su
Abstract
In this work, we demonstrated the conceptual design and controlled fabrication of a 1 D /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.