Beyond the catalyst: A robust and omnidirectional hydrophobic triple-phase architecture for ameliorating air-breathing H2O2 electrosynthesis and wastewater remediation

Abstract

On-site H2O2 electro-generation via 2-electron O2 reduction reaction (2e−-ORR) presents tremendous potential in various H2O2-based industries. Primary efforts are dedicated in synthesizing ideal catalysts, whereas this is only part of the determinants because 2e−-ORR involves an interface of gas–liquid-solid triple phases. Beyond the catalysts, comprehending and establishing an appropriate reaction microenvironment is also crucial due to its significant roles in mediating the transport of 2e−-ORR species and boosting the kinetics of 2e−-ORR. Herein, a robust and omnidirectional hydrophobic triple-phase architecture is created to ameliorate the H2O2 electro-generation by facilely and reasonably regulating the proportion between catalysts and PTFE microparticles without energy-hungry high-temperature calcination. The positive roles of the hydrophobic triple-phase architecture are primarily ascribed to the prominently enhanced O2 mass transfer towards the reaction center, full utilization of electroactive sites, still satisfactory ion mobility, electron conductivity and liquid paths, as well as extensive triple-phase reaction zones with ultrahigh 2e−-ORR activity. Under natural air diffusion without energy-hungry aeration, the cathode with proper wettability reaches a preeminent H2O2 productivity at a near-industrial current density (44.6 mg h−1 cm−2 with satisfying current efficiency of 70.2% at 100 mA cm−2) and is dependable in the long-term electrolysis stability, which almost surpasses all the previous carbonaceous air-breathing cathodes. Considering various advantages (superior performance, economy energy, low cost, facile fabrication, etc.) of the air-breathing cathode, it also exhibits prominent behavior in wastewater remediation. This study highlights the significance of interface engineering and provides valuable inspiration for similar gas-involving electrocatalytic reactions.