A unique space confined strategy to construct defective metal oxides within porous nanofibers for electrocatalysis

Integrating defective nanoparticles (NPs) into a porous one-dimensional (1D) architecture is highly desirable for electrocatalysis due to the enhanced exposure of defective sites and accelerated mass transport features, yet it is a great challenge. Here, we report the synthesis of defective metal oxide NPs interconnected with porous nanofibers via a unique space confined strategy. Central to this strategy is encapsulating Prussian blue analogue (PBA) cubes into polyacrylonitrile (PAN) nanofibers. Due to the distinct pyrolysis behaviors of PBAs and PAN (i.e., expansion outwards, and contraction inwards, respectively), PAN confers a space confined effect on the PBA-derived metal oxides during calcination in air, resulting in the formation of various lattice defects and unsaturated metal sites on the metal oxides. Consequently, with unsaturated metal sites and an advantageous architecture (i.e., 1D porous nanofibers), the resulting nanofibers with P dopants display good performance for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Notably, as bifunctional electrocatalysts, the nanofibers deliver an overall water-splitting current density of 10 mA cm(-2) at a small voltage of 1.52 V. This work paves new pathways toward utilizing distinct pyrolysis behaviours of metal-organic compounds and polymers to construct defective nanomaterials with advanced architectures.