Mott-Schottky heterojunction of Co/Co2P with built-in electric fields for bifunctional oxygen electrocatalysis and zinc-air battery

Abstract In this contribution, a high-performance bifunctional electrocatalyst composed of Co/Co2P nanoparticles encapsulated in nitrogen and phosphorus co-doped carbon nanotubes (NPCNTs) has been synthesized via a mechanochemistry-pyrolysis approach. The Schottky effect of metal-semiconductor heterojunction affords a built-in electric field at the interfaces to enhance electron transport, whereas the intertwined structure of one-dimensional (1D) NPCNTs facilitates the mass transfer of reactants and intermediates. Therefore, the as-prepared Co/Co2P@NPCNTs catalyst exhibits outstanding bifunctional ORR/OER activities, which are superior to those of commercial Pt/C and RuO2. It can also deliver a high power density and cycling life when used as the cathode for rechargeable ZABs. Theoretical calculation confirms that the spontaneous electron transport from Co to Co2P enables an up-shifted d-band center of Co/Co2P heterojunctions, which is beneficial for the intermediate adsorption in electrocatalytic process.