Direct methylhydrazine fuel cell enabled by a three-dimensional hierarchical Pd-Ni(OH)2/NF anode

This study presents a novel direct methylhydrazine fuel cell (DMHFC) utilizing a hydrothermally synthesized Pd-Ni(OH)₂ composite catalyst supported on nickel foam (Pd-Ni(OH)₂/NF) as the anode. The Pd-Ni(OH)₂/NF features a three-dimensional hierarchical architecture with dispersed Pd nanoparticles (0.08 mg cm⁻²) chemically anchored via Pd-O-Ni bonds in the Ni(OH)₂ nanosheet matrix, as confirmed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) analyses. The electrode demonstrates superior electrocatalytic activity for the methylhydrazine oxidation reaction (MHOR), attributed to enhanced active site accessibility, charge transfer efficiency, and optimized mass transport. Differential electrochemical mass spectrometry (DEMS) reveals complete oxidation of hydrazine fragments to N₂ with suppressed NH₃ byproduct formation relative to Pd/C. Systematic optimization of operating conditions yields a peak power density of 30.5 mW cm⁻² (oxygen as the oxidant, 80 °C) and 110 mW cm⁻² (hydrogen peroxide as the oxidant, 80 °C), with performance trade-offs observed between reaction kinetics and fuel crossover. This work validates the feasibility of DMHFC technology, highlighting the potential of methylhydrazine as a high-energy-density fuel for portable systems, while providing insights into electrode design and performance optimization for advanced energy conversion devices.