Nanostructured metal phosphides are a promising class of electrocatalysts for the oxygen evolution reaction (OER). Hollow nanostructured metal phosphides are expected to further enhance the electrocatalytic activity. However, they have rarely been reported.

Xiong Wen (David) Lou, Nanyang Technological University, Singapore, and colleagues have developed a metal-organic framework (MOF)-based method to synthesize nanoboxes made from carbon-incorporated nickel-cobalt mixed-metal phosphides (NiCoP/C). The team first synthesized ZIF-67@layered double hydroxide (LDH) nanoboxes using a reaction between ZIF-67 (a Co-based zeolitic imidazolate framework) nanocubes and Ni(NO₃)₂. The NiCoP/C nanoboxes were then formed by reacting ZIF-67@LDH with NaH₂PO₂ at 350 °C for two hours under a nitrogen atmosphere.

The synthesized NiCoP/C nanoboxes (pictured) exhibit enhanced electrocatalytic activity and excellent long-term stability for the OER. The researchers attribute the enhanced electrocatalytic activity to the synergistic combination of different metal phosphides, the presence of carbon, and the hollow structure.

• Carbon-Incorporated Nickel-Cobalt Mixed Metal Phosphide Nanoboxes with Enhanced Electrocatalytic Activity for Oxygen Evolution,
  Peilei He, Xin-Yao Yu, Xiong Wen David Lou,
  Angew. Chem. Int. Ed. 2017.
  DOI: 10.1002/anie.201612635