Ultrasensitive electrode-free and co-catalyst-free detection of nanomoles per hour hydrogen evolution for the discovery of new photocatalysts

High throughput theoretical methods are increasingly used to identify promising photocatalytic materials for hydrogen generation from water as a clean source of energy. While most promising water splitting candidates require co-catalyst loading and electrical biasing, computational costs to predict them a priori become large. It is, therefore, important to identify bare, bias-free semiconductor photocatalysts with small initial hydrogen production rates, often in the range of tens of nanomoles per hour, as these can become highly efficient with further co-catalyst loading and biasing. Here, we report a sensitive hydrogen detection system suitable for screening new photocatalysts. The hydrogen evolution rate of the prototypical rutile TiO₂ loaded with 0.3 wt. % Pt is detected to be 78.0 ± 0.8 µmol/h/0.04 g, comparable with the rates reported in the literature. In contrast, sensitivity to an ultralow evolution rate of 11.4 ± 0.3 nmol/h/0.04 g is demonstrated for bare polycrystalline TiO₂ without electrical bias. Two candidate photocatalysts, ZnFe₂O₄ (18.1 ± 0.2 nmol/h/0.04 g) and Ca₂PbO₄ (35.6 ± 0.5 nmol/h/0.04 g) without electrical bias or co-catalyst loading, are demonstrated to be potentially superior to bare TiO₂. This work expands the techniques available for sensitive detection of photocatalytic processes toward much faster screening of new candidate photocatalytic materials in their bare state.