Bifunctional CoP and CoN porous nanocatalysts derived from ZIF-67 in situ grown on nanowire photoelectrodes for efficient photoelectrochemical water splitting and CO2 reduction

Abstract

To develop highly efficient and non-noble metal catalysts in solar-driven photoelectrochemical cells for water splitting and CO₂ reduction is a tremendous challenge but there is a strong desire to accomplish it. Herein, CoP- and CoN-based porous nanocatalysts, which were in situ transformed from Co-based zeolitic imidazolate framework (ZIF-67), are reported as efficient co-catalysts for photoelectrochemical water splitting and CO₂ reduction. The CoP wrapped with N-doped carbon (CoP/CN) nano-electrocatalysts, with high catalytic activity and stability for both the hydrogen (HER) and oxygen (OER) evolution reactions in situ coated with TiO₂ nanowires (TiO₂ NWs@CoP/CN), and the p-type Si nanowires (Si NWs@CoP/CN) strikingly promoted photoelectrochemical water splitting by serving as a photoanode and a photocathode, respectively, whereas CoN wrapped with N-doped carbon (CoN/CN) nanocatalysts presented excellent electrocatalytic activity towards CO₂ reduction with a low onset potential, high selectivity, and good stability. It can be noted that CoN/CN catalysts-covered p-type Si nanowires (Si NWs@CoN/CN) also displayed high photoelectrochemical performance for CO₂ reduction. The superior photoelectrochemical catalytic properties can be ascribed to the synergetic effect of the porous N-doped carbon network inherited from ZIF-67 and wrapped CoP or CoN nanoparticles as well as the superior interface achieved via the in situ growth method.