Biocatalyzed Lactate Oxidation Enables Efficient Bias-Free Hydrogen Production in a Three-Chamber Reactor

The catalytic conversion of low-grade organic substrates into hydrogen offers a promising route for low-energy hydrogen production, thereby supporting sustainable resource utilization. However, realizing this potential requires efficient and robust catalysts that can operate at low overpotential. Conventional inorganic catalysts, including those based on costly precious metals, are generally plagued by high overpotentials for organic oxidation. Here, we demonstrate a unique bacteria-catalyzed lactate oxidation process for hydrogen production using a three-chamber reactor. This three-chamber system integrates a neutral bacteria-driven anolyte, a basic electrolyte bridge, and an acidic catholyte to achieve low-overpotential lactate oxidation coupled with efficient hydrogen evolution. The system enables simultaneous bias-free hydrogen generation and power output, reaching a peak current of ∼13 mA cm^-2, with an electricity generation of ∼0.22 kWh per cubic meter of H₂ at 10 mA cm^-2. The system maintains stable operation for over 1000 h at 10 mA cm^-2 with a high Coulombic efficiency (∼95%) and near-unity Faradaic efficiency for H₂ production (∼99%). Moreover, we show that this system can effectively leverage acidic and alkaline waste from semiconductor processing to enable bias-free hydrogen production, advancing low-emission electrolysis technologies for a sustainable hydrogen economy.