Polyoxometalate‐Based Single‐Atom Catalyst with Precise Structure and Extremely Exposed Active Site for Efficient H 2 Evolution

Single-atom catalysts with precise structure and extremely high catalytic efficiency remain a fervent focus in the fields of materials chemistry and catalytic science. Herein, a nickel-substituted polyoxometalate (POM) {NiSb₆O₄(H₂O)₃[β-Ni(hmta)SbW₈O₃₁]₃}^15- (NiPOM) with one extremely exposed nickel site [NiO₃(H₂O)₃] was synthesized using the conventional aqueous method. The uniform dispersion of single nickel center with well-defined structure was facilely achieved by anchoring nanosized NiPOM on graphene oxide (GO). The resulting NiPOM/GO can couple with CdS photoabsorber for the construction of low-cost and ultra-efficient hydrogen evolution system. The H₂ yield can reach to 2753.27 mmol g_POM ^-1 h^-1, which represents a record value among all the POM-based photocatalytic systems. Remarkablely, an extremely high hydrogen yield of 3647.28 mmol g_POM ^-1 h^-1 was achieved with simultaneous photooxidation of commercial waste plastic, representing the first POM-based photocatalytic system for H₂ evolution and waste plastic conversion. This work highlights a straightforward strategy for constructing extremely exposed single-metal site with precise microenvironment by facilely manipulating nanosized molecular cluster to control individual atom.