Catalytic hydrogen generation from non-food-feed biomass is pivotal for carbon-neutral economy, which is limited by low hydrogen productivity, high CO concentration, and excessive fossil energy consumption. Herein, we demonstrate a synergistic effect between Ni²⁺ single atoms and metallic Ni nanoparticles supported on La₂O₂CO₃ (Ni_SA+NP/La₂O₂CO₃), which attains a fermentation broth reforming with a stable hydrogen production rate of 2373 mmol·g⁻¹·h⁻¹ and ~ 99.6% hydrogen purity at 550 °C, notably higher than the counterparts. Theoretical calculations reveal that the multiscale effect of Ni²⁺ single atoms and metallic Ni nanoparticles can promote the dissociation of C–C/C–H bonds to enhance the organics decomposition and strengthen the CO adsorption as well as water gas shift reaction to reduce the CO concentration in hydrogen gas. Combined with photothermal reactor, the natural sunlight driven photothermal fermentation broth reforming over Ni_SA+NP/La₂O₂CO₃ achieves 1129 mmol·g⁻¹·h⁻¹ of hydrogen evolution rate, > 99.6% hydrogen purity and an enthalpy change solar-to-hydrogen efficiency of 16.6%, that outperforms the 10% commercial utilization target set by the US Department of Energy. This work offers a novel perspective for the development of sunlight driven fermentation broth reforming through the ingenious design of synergistic catalytic sites.