Solar photo-thermocatalytic valorization of biomass waste to biofuel precursors using inexpensive Ni–P/graphite catalysts

Developing efficient, low-cost catalytic routes for biomass upgrading for sustainable fuel and chemical production is a crucial step toward a greener society and circular economy. Ni–P/graphite catalysts prepared by electroless deposition on graphite microflakes were used for photo-thermocatalytic transfer hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in isopropanol, without external H 2 or noble metals. Graphite provides broadband optical absorption and localized heat generation; the Ni P coating supplies the active hydrogen-transfer sites, with isopropanol serving as hydrogen donor. Under near-infrared laser irradiation at 105 °C, complete LA conversion was achieved in 120 min, 2.5-fold faster than the solvothermal process at the same temperature. Solar-driven tests using a parabolic concentrator (105 °C, 2.5 mg mL −1 , 100 mL scale) yielded 99.1% GVL after 80 min; over-reduction to valeric acid became significant only at 120 min. The catalyst retained near-quantitative activity over five consecutive cycles with negligible cumulative Ni and P leaching. Tests with a synthetic biomass hydrolysate approximating wheat-derived acid hydrolysate composition (LA/furfural/formic acid, 104:1:36 M ratio) showed LA conversion exceeding 99.9% at 40 min and complete furfural conversion by 80 min. The furfural hydrogenation network yielded furfuryl alcohol, 2-methylfuran, tetrahydrofurfuryl alcohol, and 2-methyltetrahydrofuran (23.2% at 120 min). Formic acid decomposition supplemented isopropanol as hydrogen donor under mixed-feed conditions. The optimal catalyst loading of 2.5 mg mL −1 was 36-fold lower than the Raney Ni dose required for comparable photo-thermocatalytic LA conversion, which additionally demanded a reaction temperature of ca. 130 °C.