0D/2D heterojunctions via the single-photon excitation can avoid the light shielding of non-active component to promote the photocatalytic activity. However, it is very difficult to prepare ultrasmall nanoparticles loaded on 2D nanosheets via one pot method. Heren, we fabricated a Nb2O5/ZnIn2S4 (Nb-ZIS) heterojunction via a simple solvothermal process assisted by the Na2CO3 and thioacetamide (TAA), where zero-dimensional (0D) ultra-small Nb2O5 particles (≈10 nm) are uniformly in-situ grown on two-dimensional (2D) ZnIn2S4 nanosheets (ZIS). Structural characterizations and density functional theory (DFT) calculation suggest that the 0D-on-2D interface can not only alleviate the blocking effect of light, promoting light absorption for photocatalytic process, but also enhances the separation of photon-generated carriers through the built-in electric field (BIEF). Encouragingly, the Nb-ZIS heterojunction shows significant enhancement for H2 evolution and degradation of lignin, where the hydrogen evolution rate reaches 5.4 mmol h−1 g−1 and the lignin degradation rate achieves 78.5%, surpassing the commercial block Nb2O5 supported on ZIS heterojunction (Nb-ZIS-C) (4.0 mmol h−1 g−1 for hydrogen evolution and 61.9% for degradation) and the 0.2Nb/ZIS without the addition of Na2CO3 (4.5 mmol h−1 g−1 for hydrogen evolution and 72.3% for degradation), respectively.