Porous Membrane Electrode Assembly for Electrosynthesis of High‐Purity and High‐Concentration Hydrogen Peroxide

ABSTRACT Hydrogen peroxide (H 2 O 2 ) is an environmentally benign oxidant with broad applications in chemical synthesis, environmental remediation, and disinfection. Electrochemical production via the two‐electron oxygen reduction reaction (2e − ORR) offers a sustainable alternative to the traditional energy‐intensive process. However, achieving high concentrations under electrolyte‐free conditions remains challenging due to limited selectivity, mass‐transport constraints, and high operating voltages. Here, we report a porous proton exchange membrane (PEM)–based electrochemical cell (5 cm × 5 cm) that enables efficient and durable H 2 O 2 production. Among various porous substrates, glass‐fiber filters retained dimensional stability after Nafion ionomer loading and provided uniform proton‐conduction pathways, balancing proton conductivity and oxygen gas permeability in the porous PEM. Acid‐treated Co single‐atom catalysts dispersed in hydrophilic SiO 2 particles enhanced intrinsic 2e − ORR selectivity and catalyst‐layer wettability, resulting in a H 2 O 2 Faradaic efficiency above 75% at 100 mA cm −2 at a cell voltage of ∼2.3 V. The porous PEM‐based cell produced electrolyte‐free H 2 O 2 solutions up to 12 wt.% (3.6 mol L −1 ) and operated stably for over 100 h, demonstrating its potential as a platform for practical H 2 O 2 electrosynthesis.