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

Abstract

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 sunlightdriven dehydrogenation and hydrogenolysis of benzyl alcohol. The heterostructure 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 CdS 0.4 Se 0.6 -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 biomassrelevant substrates. KeywordsAlcohol dehydrogenation, Benzyl alcohol, CdS, photo-catalytic, photo-induced, product distributions, renewable energies, renewable fuels, semiconductor metals, tandem catalysis, transfer hydrogenations, biomass, cadmium compounds, hydrolysis ABSTRACT: 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 heterostructure 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 CdS 0.4 Se 0.6 -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. SECTION: Energy Conversion and Storage; Energy and Charge Transport S olar-to-chemical energy conversion of biomass is a

Efficient electrostatic self-assembly of one-dimensional CdS–Au nanocomposites with enhanced photoactivity, not the surface plasmon resonance effect

“…39 In recent years, a new class of colloidal nanoheterostructures containing both 1-D semiconductor nanostructures and metallic domains has been prepared. [22][23][24][25]31,[46][47][48][49] For example, Lian and co-workers have investigated the mechanism of exciton quenching and charge separation in the CdS-Pt nanorod heterostructure by using ultrafast transient absorption spectroscopy. [22][23][24][25]31,[46][47][48][49] For example, Lian and co-workers have investigated the mechanism of exciton quenching and charge separation in the CdS-Pt nanorod heterostructure by using ultrafast transient absorption spectroscopy.…”

“…31 They have proven that the excitons in the CdS domain dissociate by ultrafast electron transfer to Pt and the charge separated state is surprisingly long-lived due to the trapping of holes in CdS. 46 They have proven that photochemically generated, surface-adsorbed CdS nanorod-Pd-H equivalents are useful synthetic intermediates in tandem catalysis via transfer hydrogenation. 46 They have proven that photochemically generated, surface-adsorbed CdS nanorod-Pd-H equivalents are useful synthetic intermediates in tandem catalysis via transfer hydrogenation.…”

“…31 Vela and co-workers have shown that CdS nanorod-M (M ¼ Pt, Pd) heterostructures are active catalysts for room-temperature photochemical dehydrogenation and hydrogenolysis of an alcohol. 46 However, specic studies on the photocatalytic performance of such 1-D semiconductormetal nanocomposites are still relatively scarce. 46 However, specic studies on the photocatalytic performance of such 1-D semiconductormetal nanocomposites are still relatively scarce.…”

Selenium Redox Reactivity on Colloidal CdSe Quantum Dot Surfaces

“…17 Alcohols such as ethanol have been shown to photodope metal-oxide NCs (e.g., ZnO) 8,18−23 and have been used as sacrificial reductants for semiconductor–metal heterostructure photocatalysis. 24−26 ( ii ) Cd 2+ centers on the QD surfaces could be reduced to Cd 0 . This reduction has been proposed to be a key step for CdSe photocatalysis.…”

Photocatalytic hydrogenolysis of allylic alcohols for rapid access to platform chemicals and fine chemicals

“…As hydrogen atom(s) from methanol is incorporated in the alkene product in the photocatalytic process, we characterized this reaction as photocatalytic transfer hydrogenolysis (PcTH) [17,18]. The PcTH of allyl alcohols is highly chemo-and redox-selective: hydrogenolysis of the C-O σ-bond predominates over reduction of the C=C π-bond and oxidation of the HC-OH bond.…”