MOF-derived nanostructured cobalt phosphide assemblies for efficient hydrogen evolution reaction

The earth-abundant metal phosphides have emerged as new and active alternatives for the precious metal platinum to electrocatalyze the hydrogen evolution reaction (HER) via water splitting. In this study, we report on the straightforward and controllable synthesis of various nanostructured cobalt phosphide assemblies through the direct chemical transformation of a Co-containing metal-organic framework (ZIF-67-Co) under mild phosphorization conditions. The resulting CoP nanoparticle assemblies (NPAs) and nanorod assemblies (NRAs) can be selectively produced by rationally tuning the calcination atmosphere. The CoP NRAs were found to be highly active for electrocatalytic hydrogen generation, which exhibited better performance than that of the CoP NPAs, as evidenced by their relatively low onset overpotential (similar to 86 mV), small Tafel slope (similar to 69 mV dec (1)) and long-term stability in acidic media.