Selective Alcohol Dehydrogenation and Hydrogenolysis with Semiconductor-Metal Photocatalysts: Toward Solar-to-Chemical Energy Conversion of Biomass-Relevant Substrates

Photocatalytic conversion of biomass is a potentially transformative concept in renewable energy. Dehydrogenation and hydrogenolysis of biomass-derived alcohols can produce renewable fuels such as H-2 and hydrocarbons, respectively. We have successfully used semiconductor-metal heterostructures for sunlight-driven dehydrogenation and hydrogenolysis of benzyl alcohol. The hetero-structure composition dictates activity, product distribution, and turnovers. A few metal (M = Pt, Pd) islands on the semiconductor (SC) surface significantly enhance activity and selectivity and also greatly stabilize the SC against photoinduced etching and degradation. Under selected conditions, CdS-Pt favors dehydrogenation (H-2) over hydrogenolysis (toluene) 8:1, whereas CdS0.4Se0.6-Pd favors hydrogenolysis over dehydrogenation 3:1. Photochemically generated, surface-adsorbed hydrogen is useful in tandem catalysis, for example, via transfer hydrogenation. We expect this work will lead to new paradigms for sunlight-driven conversions of biomass-relevant substrates.