Photocatalytic production of H2 is a multi-criteria optimization problem: Case study of RuS2/TiO2

Many parameters influence the photocatalytic production of H2. Identifying and quantifying them is necessary for correct comparison of photocatalysts and right understanding of involved mechanism. In this work, we studied the photocatalytic dehydrogenation of isopropanol with titania-supported ruthenium disulfide. We studied the influence of seven parameters on the photocatalytic activity: the temperature, the composition of the reactive mixture, the mass of the photocatalyst, the flux and the energy of the incident photons, the co-catalyst loading and the nature of the support. Their influence was studied, not only on the rate of hydrogen production (or photon yield) but also on the apparent activation energy and on the pre-exponential factor, deduced from an Arrhenius law. The photon yield as a function of the co-catalyst loading show an optimum of activity. A 6.9 % photon yield was obtained at 0.84 wt% and Ephotons = 3.65 eV. The rate-determining step for the photocatalytic dehydrogenation of the isopropanol with RuS2/TiO2 is, at optimal conditions, the electron transfer from TiO2 to RuS2. The latter is not favored because of the band diagrams of RuS2 and TiO2. The electron transfer can be optimized working with incident photons having a higher energy, thanks to a hot carrier effect observed in RuS2/TiO2.

Automated summary

This study investigated the influence of seven parameters on the photocatalytic production of hydrogen, including the optimal electron transfer from TiO2 to RuS2 at the rate-determining step. The photon yield showed an optimum at specific co-catalyst loading level, demonstrating the potential for optimizing electron transfer with incident photons having higher energy levels.