Electrochemical fabrication of porous NiCuMoO_x electrodes to enhance mass transfer in anion exchange membrane water electrolyzers

The development of efficient non-noble electrocatalysts for alkaline hydrogen evolution reactions requires balancing intrinsic activity, structural stability, and mass transfer. This study demonstrates the electrodeposition of ternary NiCuMoO_x composites on carbon paper to utilize the advantages of both the binary Ni-Mo and Ni-Cu systems. Structural characterization revealed that the optimized NiCuMoO_x/carbon paper (CP) exhibits an intermediate morphology between the film-like NiMoO_x/CP and dendritic NiCuO_x/CP, featuring a face-centered cubic NiCu crystalline phase, as confirmed by X-ray diffraction and high-resolution transmission electron microscopy. Electrochemical evaluations in half-cell configurations show that NiCuMoO_x/CP achieves a remarkably low hydrogen evolution reaction overpotential of 36 mV at −10 mA cm−2 and a Tafel slope of 86 mV dec−1. Under conditions of high current density (>400 mA cm−2), the dendritic NiCuMoO_x/CP exhibits superior mass transfer owing to enhanced bubble detachment and excellent stability during 12-h chronopotentiometry tests. The anion exchange membrane water electrolyzer achieved a current density of 1.47 A cm−2 at 2.0 V_cell, attributed to synergistic reduction of kinetic and mass-transfer overpotentials enabled by Mo incorporation and a porous structure. These findings highlight the critical role of ternary composite catalyst in bridging the activity–stability trade-off for industrial-scale electrolyzers.