Bio-based superaerophobic hydrogels to regulate bubble dynamics in gas-evolving electrocatalysis

Abstract

Gas bubble accumulation is a hidden but pervasive bottleneck in electrochemical energy conversion, masking active sites, disrupting ion transport, and inflating apparent overpotentials. Here, we demonstrate a fully bio-based superaerophobic hydrogel coating, derived from chitosan crosslinked with glutaraldehyde, that transforms nickel foam electrodes into bubble–tolerant interfaces for hydrogen evolution. Systematic tuning of crosslinking density reveals that an optimal formulation (CS5GA) achieves uniform coverage, open porosity, and dynamic hydration, enabling spontaneous bubble release at subcritical radii. As a result, charge-transfer resistance is drastically reduced, overpotentials are lowered in acidic and alkaline media, and long-term stability of 40 h is preserved without altering the intrinsic HER pathway in the alkaline medium. Importantly, the hydrogel acts not as a catalyst but as a universal interfacial regulator, decoupling charge transport from bubble adhesion. This strategy establishes a sustainable materials design principle for bubble management, with broad implications beyond hydrogen evolution, extending to oxygen evolution and CO₂ reduction where gas–liquid–solid dynamics equally govern efficiency.