Efficient water oxidation through strongly coupled graphitic C3N4 coated cobalt hydroxide nanowires

Abstract

The development of low cost and durable electrocatalysts for the oxygen evolution reaction (OER) for water splitting remains a great challenge. Here, we developed strongly coupled hybrid nanowires (NWs) of anion (Cl⁻ and CO⁻) doped cobalt hydroxide coated with nanosheets of graphitic carbon nitride (Co(OH)₂@g-C₃N₄) through an in situ hydrothermal method. With 5% g-C₃N₄ added in the synthesis, we obtained perfectly coated Co(OH)₂ by g-C₃N₄ nanosheets with an overall diameter of ∼110 nm and a coating layer of ∼10 nm. The structural and compositional analyses confirm the strong interaction between g-C₃N₄ and Co(OH)₂ that makes the hybrid highly effective for the OER. As a result Co(OH)₂@g-C₃N₄ NWs exhibit an excellent over-potential of 0.32 V at 10 mA cm⁻² as well as extraordinary stability, which are better than those of the state-of-the-art noble metals (IrO₂ and RuO₂) and most reported Co- and C₃N₄-based electrocatalysts although both Co(OH)₂ and g-C₃N₄ separately display very fair performance. Furthermore, a combination of Co(OH)₂@g-C₃N₄ and Pt/C delivers a current density of 80 mA cm⁻² at 1.9 V for overall water splitting.