Triple-phase interface engineering in carbon-black gas diffusion electrodes via DMS volume-controlled modification for enhanced H₂O₂ electrosynthesis

Hydrogen peroxide (H₂O₂) electrosynthesis via the two-electron oxygen reduction reaction (2e⁻ ORR) is critically dependent on the formation of stable and well-regulated triple-phase interfaces (TPIs), where gas, liquid, and catalyst converge. However, micropore flooding and uneven wettability in carbon-black gas diffusion electrodes (GDEs) often hinder oxygen transport and deactivate active sites. In this work, we address these challenges by introducing a dimethyl silicone oil (DMS) volume-gradient strategy to engineer confined TPIs within the carbon catalyst layer. Carbon-black GDEs were prepared using DMS volume-controlled of 0.4, 0.6, and 1.2 mL, with CB-DV06 identified as the optimum configuration. This design balances hydrophobicity and pore accessibility, promoting sustained oxygen diffusion and suppressing water blockage without impeding electron or ion transport. The optimized GDE (CB-DV06) achieved ~750 mg L⁻¹H₂O₂ after 180 min with current efficiencies exceeding 60% and enhanced electrochemically active surface area. To demonstrate the practical applicability of the in situ generated H₂O₂, Reactive Black B (RBB) degradation was employed as a model pollutant-removal reaction. The integrated system achieved approximately 85% RBB decolourisation, demonstrating the applicability of this interface-engineering strategy for pollutant-removal applications. Overall, this study highlights a low-impact approach for optimizing oxygen reduction environments in porous electrodes, advancing sustainable oxidant generation and environmental remediation.