Solar Biorefinery: Stoichiometric Coproduction of Gluconic and Glucaric Acids and Impurity-Free Hydrogen from Lignocellulosic Biomass and Water

Solar biorefinery serves as a game changer in the sustainable production of transportation fuels and value-added chemicals by capitalizing on sunlight, lignocellulosic biomass, and water. Central to this endeavor is the modulation of highly reactive, nonselective hydroxyl radicals to prevent undesired side reactions. Here, surface-hydroxylated nickel oxyphosphide works synergistically with one-dimensional gallium nitride, enabling the selective reforming of lignocellulose in water toward glucose-derived organic acids (GOAs: gluconic and glucaric acids) and H2 at a nearly stoichiometric ratio: (C6H12O6)n+ H2O + sunlight → GOAs + H2. The GaN@NiOP–OH system achieves an H2 evolution rate of 2.55 mol g–1 h–1 with 100% gas-phase selectivity under simulated concentrated sunlight at 3.5 W cm–2. GOAs are simultaneously produced at a total rate of 2.23 mol g–1 h–1, corresponding to a near-stoichiometric GOAs/H2 ratio of 0.97 with nearly 100% atom utilization efficiency. This platform is broadly applicable to sunlight-driven reforming of cellulose, straw, and camphorwood. In situ spectroscopy, isotope labeling, and density functional theory calculations demonstrate that NiOP–OH cooperates with GaN to modulate in situ-generated hydroxyl radical species originating from water oxidation by photogenerated holes. These radicals are confined on the catalytic surface with their nonselective reactivity finely tuned, enabling selective conversion of glucose with H2O into GOAs and H2 via a dynamic hydroxyl exchange mechanism while suppressing side and mineralization reactions. Outdoor testing and techno-economic analysis confirm the practical viability of this proof-of-concept solar biorefinery for coproducing high-value chemicals and green H2 using only sunlight, lignocellulose, and water.