A recyclable photocatalyst: hydrogel beads with synergistic hydrophilic-hydrophobic networks for H2O2 generation

Photocatalytic hydrogen peroxide (H 2 O 2 ) production offers a sustainable route for solar-to-chemical conversion, yet practical applications are often hindered by inefficient mass transport and poor catalyst recoverability. Herein, a rationally designed resorcinol–formaldehyde/sodium alginate (RF/SA) hydrogel featuring an interpenetrating hydrophilic-hydrophobic network was proposed that synergistically enhances catalytic performance while enabling facile recycling. In this hydrogel, the hydrophobic RF regions can enrich molecular O 2 and provide photo-generated electrons, while the hydrophilic sodium alginate-polyvinylpyrrolidone (SA-PVP) network maintains a hydrated microenvironment, thereby facilitating reactant accessibility which the biphasic structure achieves a H 2 O 2 yield of up to 634 μmol g −1 h −1 in pure water, twice that of the original RF powder, while retaining significant activity in tap water and lake water. Mechanistic studies confirm a reaction pathway dominated by 2e − oxygen reduction reaction (ORR), with a minor contribution from water oxidation reaction (WOR). Crucially, the hydrogel form overcomes the agglomeration and separation limitations inherent in powder catalysts which enables facile separation and recovery, with an activity retention rate exceeding 93% after four cycles, demonstrating good reusability. This study provides a roadmap for optimizing photocatalytic hydrogen peroxide production and designing photocatalysts that combine high efficiency with practical applicability.