Making sense of hydrogen evolution

Abstract

The setup combines controlled illumination, stirring, temperature regulation, integrated temperature probing, and the amperometric hydrogen microsensor (which can be used in two complementary modes) in a sealed glass reactor (see image). When operated in the aqueous phase, the sensor follows dissolved hydrogen near the catalyst of the photocatalytic reaction during irradiation, revealing induction periods, rate changes, and possible catalyst deactivation. Quantification is performed after illumination has ceased and gas–liquid equilibration has been reached, allowing the total hydrogen produced to be derived from the equilibrated aqueous concentration, along with the known liquid and headspace volumes (the area at the top of the reactor, below the solar illuminator), and temperature. Alternatively, the sensor can be placed in the headspace after illumination and equilibration, providing an independent endpoint measurement of gas-phase hydrogen while avoiding sensor-heating artifacts from the light source. Because both modes should report the same amount of accumulated hydrogen, they provide an internal check on the entire measurement system. An agreement between the two modes strengthens confidence in the result, whereas discrepancies can indicate incomplete equilibration, leakage, or sensor perturbation. Together, these approaches help to clarify whether observed changes in activity are due to the photocatalyst itself or the measurement conditions. With this microsensor-based reactor, we aim to lower the barrier to quantitative measurements of photocatalytic hydrogen production, while ensuring experimental control and reproducibility.