Integrating distinct functional reaction sites within a single photocatalyst offers a promising approach for enhancing the photocatalytic H₂ evolution by water splitting. However, the synergy between the dual active sites is hindered by suboptimal electronic states arising from the uniform coordination environments. Here we demonstrate a strategy for enhancing the synergy between Pt single atoms and nanoparticles by modulating the coordination environment. The optimal boron doped catalyst with B-Pt-O asymmetric coordination achieves a H₂ evolution rate of 627.6 mmol g^-1h^-1, with an apparent quantum efficiency of 98.4%. Experimental and theoretical analysis reveal that the asymmetric coordination structure redistributes the electron density of Pt cocatalysts, promoting charge carrier separation, optimizing the dissociation and adsorption-desorption of the intermediate H₂O* and H* on the dual sites. The findings highlight the importance of asymmetric coordination facilitates the photogenerated carrier transfer and surface reactions for efficient photocatalytic H₂ evolution.