Noble-metal-free cobalt aerogel cathodes for HClO reduction in methanol microfluidic fuel cells

• Synthesis parameters govern CoA morphology, porosity, and oxygen incorporation. • Nodule-type CoA exhibit hierarchical porosity and high surface area. • Moderate oxygen content enhances mass transport and active site density. • Optimized CoA reaches open circuit voltage ≈1.7 V, outperforming Co-based cathodes. • CoA deliver peak power ≈20 mW cm −2 with high stability, competing with Pt catalysts. Hypochlorous acid (HClO) is a fully soluble oxidant that enables high cell voltages and power densities in methanol microfluidic fuel cells (μFCs). However, its practical implementation is limited by the lack of efficient cathode catalysts that can fully exploit its high reduction potential. In this work, we demonstrate the fabrication of self-supported cobalt aerogel electrocatalysts via a microwave-assisted sol–gel route and investigate how systematic control of synthesis parameters tunes their structural features and electrocatalytic properties. The optimized cobalt aerogel catalyst exhibits a nodular, interconnected architecture, a high specific surface area (137 m 2 g −1 ), and a moderate oxygen incorporation (O/Co ratio ≈ 1.3), resulting in improved mass transport, enhanced electrocatalytic activity, and stable operation. Used as cathodes in methanol/HClO μFCs, these materials deliver open-circuit voltages of up to 1.8 V and achieve peak power densities of ∼ 20 mW cm −2 . The performance achieved surpasses that of state-of-the-art Co-based cathodes and approaches that of noble-metal counterparts, positioning cobalt aerogels as promising next-generation cathode materials for microfluidic and other room-temperature fuel cell technologies.