Electrode materials for water splitting in alkaline electrolysis

Abstract

Alkaline water electrolysis is a leading pathway to renewable hydrogen production, yet conventional immersed-electrode systems are constrained by bubble-induced mass transport losses and sluggish reaction kinetics. This study investigates NiMo cathodes and NiFe anodes fabricated by galvanostatic electrodeposition onto stainless steel mesh substrates (#300 and #400) for operation in a capillary-fed electrolysis cell, which supplies electrolyte via capillary action through a porous separator, enabling near bubble-free operation. The influence of mesh geometry, fluoropolymer chemistry (PTFE vs. PVDF), coating morphology, gas removal efficiency, and full-cell performance was evaluated in 1 M KOH. SEM and EDS confirmed Volmer–Weber island growth on both substrates, with the #400 mesh supporting higher nucleation density and more uniform elemental distribution. Three-electrode measurements showed NiMo reduces η10 by 222 mV and NiFe reduces η100 by 72–79 mV relative to uncoated #400 substrates. In full-cell testing, the #400 PTFE configuration achieved 1.85 V at 0.5 A and 2.18 V at 1.5 A, compared to 2.49 V at 1.5 A for the polymer-free baseline. Post-operation EDS revealed severe Mo leaching in NiMo cathodes and beneficial Fe enrichment in NiFe anodes consistent with active NiFeOOH reconstruction. The results demonstrate that full-cell performance is governed by the interaction between mesh pore geometry and fluoropolymer surface energy rather than intrinsic catalyst activity alone, with the #400 mesh paired with PTFE identified as the optimal configuration within the tested parameter space.