Flower-like cobalt hydroxide/oxide on graphitic carbon nitride for visible-light-driven water oxidation

Abstract

Direct water oxidation via photocatalysis is a four-electron and multiple-proton process which requires high extra energy input to produce free dioxygen gas, making it exacting, especially under visible light irradiation. To improve the oxygen evolution reaction rates (OERs) and utilize more visible light, flower-like cobalt hydroxide/oxide (Fw-Co(OH)₂/Fw-Co₃O₄) photocatalysts were prepared and loaded onto graphitic carbon nitride (g-C₃N₄) by a facile coating method in this work. Influenced by the unique three-dimensional morphologies, the synthesized Fw-Co(OH)₂ or Fw-Co₃O₄/g-C₃N₄ hybrids reveal favorable combination and synergism reflected by the modified photoelectric activities and the improved OER performances. Attributed to its prominent hydrotalcite structure, Fw-Co(OH)₂ shows better cocatalytic activity for g-C₃N₄ modification compared with that of Fw-Co₃O₄. Specifically, 7 wt % Fw-Co(OH)₂/g-C₃N₄ photocatalyst exhibits photocurrent density 4 times higher and OER performance 5 times better than pristine g-C₃N₄. This work unambiguously promotes the application of sustainable g-C₃N₄ in water oxidation.