Effect of infill density and geometry of direct ink written 3D Ni-based electrodes on their oxygen evolution reaction performance

Abstract

Abstract In this work, Direct Ink Writing (DIW) is used to develop novel complex 3D electrodes for water splitting, specifically for the oxygen evolution reaction (OER). The main advantages of using 3D electrodes for this application are to maximise catalyst surface area and facilitate gas products evacuation. High-solids-load (79 wt%), water-based pastes based on micrometer Ni powders were processed by a sequence of DIW, sintering and NiFe electrodeposition. Three different complex geometries, i.e., two rectilinear infills (40% and 55% infill density) and one gyroid infill (50% infill density), were developed as proof of concept to determine the influence of the electrode design on the OER performance. The study has demonstrated that lower infill rates (40% rectilinear infill) clearly enable OER efficiency optimisation. In addition to the higher mesh size, the superior performance of this particular electrode is enhanced by the filament orientation at 45° to the gravity vector, which facilitates buoyancy-driven bubble release, and by the inner porosity of the filaments, which is expected to favour the electrode wettability and aerophobicity.