P, N co-doped hollow carbon nanospheres prepared by micellar copolymerization for increased hydrogen evolution in alkaline water

The design of cost-effective and efficient metal-free carbon-based catalysts for the hydrogen evolution reaction (HER) is of great significance for increasing the production of clean hydrogen by the electrolysis of alkaline water. Precise control of the electronic structure by heteroatom doping has proven to be efficient for increasing catalytic activity. Nevertheless, both the structural characteristics and the underlying mechanism are not well understood, especially for doping with two different atoms, thus limiting the use of these catalysts. We report the production of phosphorus and nitrogen co-doped hollow carbon nanospheres (HCNs) by the copolymerization of pyrrole and aniline at a Triton X-100 micelle-interface, followed by doping with phytic acid and carbonization. The unique pore structure and defect-rich framework of the HCNs expose numerous active sites. Crucially, the combined effect of graphitic nitrogen and phosphorus-carbon bonds modulate the local electronic structure of adjacent C atoms and facilitates electron transfer. As a result, the HCN carbonized at 1100 °C exhibited superior HER activity and an outstanding stability (70 h at a current density of 10 mA cm⁻²) in alkaline water, because of the large number of graphitic nitrogen and phosphorus-carbon bonds.