Work

An Ultrathin Embedded SnO2 Interface for Water Dissociation in Bipolar Membranes and pseudo-PEM Electrolyzers

Year: 2026

Type: preprint

Abstract: Water dissociation (WD) at bipolar membrane (BPM) junctions is a key reaction in a number of electrochemical energy conversion and separation technologies. While metal oxide catalysts like SnO 2 accelerate WD, conventional particle-based deposition methods typically yield thick and morphologically heterogeneous junction layers. We report a simple aqueous precursor-treatment route that reconstructs the near-surface region of Nafion into an ultrathin SnO 2 -bearing interface. In contrast to conventional spin-coated SnO 2 , which forms a discrete particulate overlayer, the embedded interface is smooth, spatially confined, and closely integrated with the membrane. Despite this major structural difference, BPMs fabricated from SnO 2 -eb-Nafion exhibit WD performance comparable to benchmark spin-coated SnO 2 junctions. When normalized by SnO 2 loading, the embedded junction delivers a ~21-fold higher current density in an electrolyzer test cell at a total cell voltage of 2 V, highlighting improved catalyst utilization. Structural and electrochemical controls show that the high activity arises from interfacially localized SnO 2 rather than bulk SnO 2 incorporation or altered proton conductivity. The embedded route improves precursor efficiency, increases membrane junction adhesion force by 7×, and maintains stable operation under continuous elec-trolyzer testing. A preliminary pseudo-PEM water-electrolysis demonstration further shows that the embedded SnO 2 interface remains beneficial in an AEI–PEM heterojunction architecture coupled to a PGM-free Co 3 O 4 anode. These results establish precursor-based interfacial self-reconstruction as a practical route to thin, active, and mechanically integrated catalyst–membrane junctions. Keywords: Bipolar membranes; Water dissociation; Tin oxide (SnO 2 ); Ionomer interfaces; Water electrolysis

Source: ChemRxiv

DOI: 10.26434/chemrxiv.15009776/v1