Lignocellulose is Earth’s most abundant form of biomass and its valorization to H2 is a key objective for the generation of renewable fuels. Solar-driven photocatalytic reforming of lignocellulose to H2 at ambient temperature offers a sustainable route towards this goal, but this reaction is currently limited to noble-metal-containing systems that operate with low activity under ultraviolet light. Here, we report the light-driven photoreforming of cellulose, hemicellulose and lignin to H2 using semiconducting cadmium sulfide quantum dots in alkaline aqueous solution. We show that basic conditions cause these dots to become coated with oxide/hydroxide in situ, presenting a strategy to improve their photocatalytic performance. The system operates under visible light, is stable beyond six days and is even able to reform unprocessed lignocellulose, such as wood and paper, under solar irradiation at room temperature, presenting an inexpensive route to drive aqueous proton reduction to H2 through waste biomass oxidation.
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This work was supported by the Christian Doppler Research Association (Austrian Federal Ministry of Science, Research and Economy and the National Foundation for Research, Technology and Development), the OMV Group (to E.R.), the EPSRC (DTA studentships for D.W.W. and T.E.R), the Isaac Newton Trust, the German Research Foundation (to M.F.K.), the World Premier Institute Research Center Initiative (WPI), MEXT, Japan (to K.L.O.) and a Marie Curie Research fellowship (to K.H.L., GAN 701192 - VSHER). We would like to thank Mr Adam Brown (Cambridge, UK) for performing XPS measurements, Prof. Peter Hildebrandt (TU Berlin, Germany) for providing access to his laboratory to record Raman spectra and Dr Benjamin Martindale for proofreading this manuscript.
Patent applications covering this work have been filed by Cambridge Enterprise (UK patent application numbers GB1619953.1 and GB1701130.5) that name D.W.W., M.F.K., K.L.O. and E.R. as inventors.
Supplementary Tables 1–10, Supplementary Figures 1–14. (PDF 1688 kb)
Video of the reported system evolving H2 in the presence of a cutting from a wooden branch or paper. 3.6 nmol of ligand-free CdS QDs in DMF are injected onto each substrate and dried. The substrate was then added to 2 ml of 10 M KOH, forming CdS/CdOx. Samples were purged with N2 and irradiated using simulated solar light (AM 1.5G, 100 mW cm−2) for 1 h before filming. Filming was undertaken while irradiating with light from a nearby Kodak carousel 2020 projector. (MP4 116522 kb)
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Wakerley, D., Kuehnel, M., Orchard, K. et al. Solar-driven reforming of lignocellulose to H2 with a CdS/CdOx photocatalyst. Nat Energy 2, 17021 (2017). https://doi.org/10.1038/nenergy.2017.21
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