Photo-/thermal synergies in heterogeneous catalysis: Towards low-temperature (solar-driven) processing for sustainable energy and chemicals

There is growing recognition that cooperative effects exist under dual-mode (photo-thermal) heterogeneous catalytic excitation that offer genuine prospects in the transition to a sustainable energy and chemicals economy. Solar beams can act as practical combined source of photons and heat (via non-radiative relaxation after optical absorption) and lead to process intensification. This review provides a critical update and appraisal of advances in photo-/thermal synergies in catalysis, now a burgeoning field. It begins by classifying possible co-excitation synergies now driving a paradigm shift in catalyst design towards inclusion of pan-spectral absorbers, e.g., narrow-gap semiconductors and/or plasmonic nanoparticulate metals. Photo-thermo- (micro)reactors and concentrators are surveyed and the photophysics of electronic excitation is briefly outlined. Emphasis is on the impact of dual-mode excitation on selected processes of importance in tomorrow's solar-biorefineries, i.e., process hydrogen generation by oxygenate(s) reforming, specialty compounds by oxygenates conversion, CO2 reduction/hydrogenation for solar fuels, and Fischer-Tropsch synthesis for renewable hydrocarbons.