Interface-induced contraction of core–shell Prussian blue analogues toward hollow Ni-Co-Fe phosphide nanoboxes for efficient oxygen evolution electrocatalysis

Hollow metal phosphides play an important role in electrocatalytic oxygen evolution reaction (OER), but directly phosphatizing solid precursors into well-defined hollow structures and further regulating electronic structures of their derived (oxy)hydroxides for boosting OER performance remain great challenges. Herein, we report hollow Ni-Co-Fe phosphide (Ni-Co-Fe-P) nanoboxes with well-defined interior spaces via a core–shell Prussian blue analogue (PBA)-dependent conversion. Starting from Ni-Co PBA nanocubes, a chemical reduction and decomposition process is utilized to fabricate core–shell Ni-Co@Fe PBA nanocubes based on the lattice matching principle, which are then phosphatized into hollow Ni-Co-Fe-P nanoboxes through an interface-induced contraction process. Thanks to well-designed hollow structures, polymetallic compositions, and doping of carbon, hollow Ni-Co-Fe-P nanobox catalyst shows a remarkable OER activity with a small overpotential of 277 mV at 20 mA cm−2. Notably, this catalyst is also highly stable with only 5 % activity decay over 24 h for the OER. Mechanism studies reveal that the electronic regulation of precatalyst-derived (oxy)hydroxides is the key to boost their OER activity. This work demonstrates a novel and effective protocol for designing polymetallic phosphides with well-defined hollow structures towards various targeted applications.