Metal-oxo Cluster Mediated Atomic Rh with High Accessibility for Efficient Hydrogen Evolution

Achieving single-atom catalysts (SACs) with high metal content and outstanding performance as well as robust stability is critically needed for clean and sustainable energy. However, most of the synthesized SACs are undesired on the loading content of the metal due to the anchored metals and the supports as well as the synthesizing methods. Herein, a Rh-SAC with high accessibility by loading it on the metal nodes of metal-porphyrin-based PCN MOFs (PCN-224) as supporting material is reported. Significantly, the PCN-Rh_15.9 /KB catalyst with a high Rh content of 15.9 wt% exhibits excellent hydrogen evolution activity with a low overpotential of 25 mV at a current density of 10 mA cm^-2 and a mass activity of 7.7 A mg^-1 _Rh at overpotential of 150 mV, which is much better than that of the commercial Rh/C. Various characterizations reveal the Rh species is stabilized by the metal nodes bearing -O/OH_x in MOFs, which is of importance for the high loading amount and the good activity. This work establishes an efficient approach to synthesize high content SACs on the nodes of MOFs for wide catalyst design.