Sustainable H₂ generation from water splitting by solar-driven photocatalysis has been proposed as a promising alternative to increasingly reduced fossil fuels. However, such techniques still face great challenges in dynamics and thermodynamics. Biomass as a hole sacrificial agent is conducive to the generation of H₂. Local surface plasmon resonance (LSPR) can effectively use solar energy and convert it into high-energy "hot carriers", and realize high efficiency solar energy to chemical energy conversion. Copper alloy inherits the LSPR effect of copper particles. Palygorskite (Pal) is a natural hydrated magnesium silicate mineral with large surface area and certain acid sites. In this work, Pal-loaded plasma alloy nanocomposite was prepared for photocatalytic reforming cellulose for synergistic hydrogen production. The phosphate group-modified Pal provides a large number of acidic sites for cellulose hydrolysis and glucose. At the same time, the LSPR effect of CuNi alloy increases the reaction temperature, realizes the photothermal cooperative catalysis, and further enhances the catalyst activity.

2 g Pal was evenly dispersed in 100 ml phosphate solution, then the mixture was stirred in an 80℃ water bath for 12 h. Thereafter, they were washed with deionized water and dried at 80℃ for 16 h to obtain H-Pal. 0.1 mol of CuCl₂·2H₂O and 0.1 mol Ni(NO₃)₂·6H₂O were dissolved in 30 ml of sodium hydroxide solution, and various-Pal was added with 0.5 g ethylenediamine by stirring. About 1 mol of sodium phosphates was added to the solution, and the mixture was transferred to the reaction kettle, reacted at 180℃ for 90 min, and then naturally cooled to room temperature. After washing, CuNi/H-Pal composite was obtained after vacuum drying for 6 h.

The photocatalytic reforming cellulose was produced under simulated sunlight. The conversion of cellulose reached a maximum of 82% for 30% CuNi/H-Pal. In the end product of photoreforming cellulose, the content of formic acid dominated, reaching the highest 36.8 μ mol · g^-1 · h^-1, followed by lactic acid 13.8 μmol·g^-1·h^-1. After the conversion of cellulose into glucose, the C—C bond in glucose finally breaks to generate formate. Compared with Cu/H-Pal and Ni/H-Pal, the CuNi/H-Pal hydrogen production efficiency is higher, because the synergistic action of bimetals can effectively promote charge separation, while retaining the LSPR effect of copper particles, thus achieving the photothermal cooperative catalysis, and the highest hydrogen evolution rate is 1.68 mmol·g^-1·h^-1.

In the aqueous solution, cellulose is first adsorbed on the surface of Pal rod crystals, and under light irradiation, photogenerated electrons reduce H⁺ to H₂ in water at the reduction end of CuNi/H-Pal. Due to the plasmon resonance effect of CuNi, CuNi/H-Pal has a significant photothermal effect, and the activity of acidic sites on the catalyst is enhanced under the synergistic effect of photothermal interaction, which promotes the cleavage of cellulose β-1,4-glycosidic bond and hydrolysis to glucose. Subsequently, the resulting glucose is converted to C5 sugar and formic acid by hole oxidation, and C5 sugar is converted to C4 sugar and formic acid through the Ruff degradation mechanism, and all intermediates are further gradually converted to formic acid through the C1-C2 α-splitting process. At the same time, cellulose conversion products contain small amounts of lactic acid. Cu on the surface of the catalyst acts as a small amount of Lewis acid active site during the catalytic reaction, promoting the conversion of glucose to lactate under the joint action of holes.

In summary, a new plasma-metal-alloy supported by clay mineral nanocomposite material was prepared. Different amounts of CuNi alloys were loaded on the surface of phosphorylated Pal, which not only retained the plasmon resonance effect of Cu element, but also improved its stability and inhibited its oxidation, and significantly improved the charge transfer efficiency due to the Schottky junction formed by the metal alloy and modified Pal. The hydrogen production rate with 30% CuNi/H-Pal catalyst could reach 1.68 mmol g^-1·h^-1 under simulated sunlight irradiation. At the same time, cellulose was converted into high value-added formic acid and lactic acid, and the yields reached 36.8 μmol·g^-1·h^-1 and 13.8 μmol·g^-1·h^-1, respectively. This work provides a new strategy for hydrogen production and the production of valuable biochemicals through biomass photocatalytic reforming.