A cage-confinement strategy to fabricate Pt-Mo6Co6C heterojunction for highly efficient PH-universal hydrogen evolution

Electrochemical water splitting has been highly considered as a promising technology to produce hydrogen with high purity and large quantity. Herein, a cage-confinement strategy is proposed to encapsulate H3PMo12O40 clusters into cavities of ZIF-67. The ZIF-67 with cavity diameter of 1.16 nm and cavity window of 0.34 nm can appropriately confine H3PMo12O40 with diameter of 1.0 nm. The H3PMo12O40 served as guest species were also homogeneously encapsulated in well-defined cavities of ZIF-67 host without destroying the structure of ZIF-67. This cage-confinement strategy endow Mo6Co6C nanoparticles uniformly embedded in carbon matrix without aggregation and exposed abundant active sites during pyrolysis process. Furthermore, the heterojunction of Pt-Mo6Co6C was fabricated through galvanic replacement with H2PtCl6. The prepared Pt-PMo/ZIF-67-800 electrocatalyst with a low Pt amount of 3.0 % exhibits excellent HER activity and stability and even superior to commercial Pt/C in PH-universal solutions. Density functional theory (DFT) calculation reveals that Pt-Mo6Co6C heterostructure results in a lower hydrogen adsorption free energy than commercial Pt/C and thus enhances its intrinsic catalytic activity. The outstanding HER performance of Pt-Mo6Co6C heterostructure confined on dodecahedron carbon matrix opens new perspectives for rational design polyoxometalate (POM) based catalyst for hydrogen evolution.