Metal-Phosphide-Containing Porous Carbons Derived from an Ionic-Polymer Framework and Applied as Highly Efficient Electrochemical Catalysts for Water Splitting

A novel phosphorus-containing porous polymer is efficiently prepared from tris(4-vinylphenyl)phosphane by radical polymerization, and it can be easily ionized to form an ionic porous polymer after treatment with hydrogen iodide. Upon ionic exchange, transition-metal-containing anions, such as tetrathiomolybdate (MoS₄ ^2-) and hexacyanoferrate (Fe(CN)₆ ^3-), are successfully loaded into the framework of the porous polymer to replace the original iodide anions, resulting in a polymer framework containing complex anions (termed HT-Met, where Met = Mo or Fe). After pyrolysis under a hydrogen atmosphere, the HT-Met materials are efficiently converted at a large scale to metal-phosphide-containing porous carbons (denoted as MetP@PC, where again Met = Mo or Fe). This approach provides a convenient pathway to the controlled preparation of metal-phosphide-loaded porous carbon composites. The MetP@PC composites exhibit superior electrocatalytic activity for the hydrogen evolution reaction (HER) under acidic conditions. In particular, MoP@PC with a low loading of 0.24 mg cm^-2 (on a glass carbon electrode) affords an iR-corrected (where i is current and R is resistance) current density of up to 10 mA cm^-2 at 51 mV versus the reversible hydrogen electrode and a very low Tafel slope of 45 mV dec^-1, in rotating disk measurements under saturated N₂ conditions.