Boosting Both Chemical and Electrochemical Tandem Steps in Low‐Potential Aldehyde Oxidation for Solar‐Driven Bipolar Hydrogen Production

Low‐potential aldehyde oxidation offers an energy‐efficient anodic alternative to oxygen evolution for bipolar hydrogen production coupled with biomass valorization, yet the tandem non‐Faradaic/Faradaic mechanism remains poorly understood. Here, we report PtCu 3 ‐coated Cu nanowire arrays supported on Cu foam (PtCu 3 @Cu/CF) fabricated via galvanic replacement and electrochemical reduction. In situ ATR‐FTIR and DFT calculations indicate the PtCu 3 shell enhances adsorption of the gem ‐diolate intermediate while weakens binding of 5‐hydroxymethyl‐2‐furancarboxylic acid (HMFCA), accelerating both non‐Faradaic C–H cleavage and Faradaic oxidation. This enables selective 5‐hydroxymethylfurfural upgrading with anodic hydrogen evolution at 300 mA cm −2 at ∼0.21 V in a two‐electrode flow electrolyzer. Additionally, the electrolyzer also achieves 100 mA cm −2 at 0.16 V with 200% combined Faradaic efficiency for bipolar hydrogen production. Integration of a six‐cell stack with perovskite photovoltaic module yields a bias‐free solar‐to‐hydrogen efficiency of 16.9% alongside gram‐scale HMFCA production. This noble‐metal‐lean platform establishes scalable solar reforming for co‐generating green hydrogen and value‐added chemicals.