One-pot synthesis of delafossite CuCoO₂ microcrystal as visible-light-driven photocatalyst

The exploration of novel photocatalyst is one of the important directions of developing efficient photocatalysis technology. Delafossite CuCoO₂ has unique crystal structure, suitable band gap and energy band edge, and excellent catalytic activity, which is a new photocatalyst well worth developing. However, the as-prepared CuCoO₂ samples in literature often have the problems of containing impurity or secondary phases, non-stoichiometry, leading to some controversies about its fundamental physicochemical properties. Moreover, there is also insufficient understanding of the use of CuCoO₂ as a novel photocatalyst. Herein, one-pot hydrothermal method was used to prepare stoichiometric delafossite CuCoO₂ microcrystals (~ 3.65 μm) with high purity and single-phase. Then, its detailed fundamental physicochemical properties as photocatalyst are further provided by a series of experimental characterization and density functional theory calculations. The results show that delafossite CuCoO₂ exhibit outstanding semi-metallic ferromagnetism, multiple electron transitions caused by various band gap types, multi band absorption and full spectrum absorption, and has appropriate band edge position, which can be applied to HER and OER of water splitting. The photocatalytic performance of CuCoO₂ was systematically tested for the first time by photocatalytic degradation of tetracycline hydrochloride, photocatalytic water-splitting, and photocurrent measurement in PEC cell. Under visible light irradiation, the as-prepared CuCoO₂ can degrade more than 90% of tetracycline hydrochloride within 4 h. Without sacrificial agent and cocatalyst, the shows the hydrogen and oxygen evolution rates from photocatalytic water-splitting of as-prepared CuCoO₂ reached to 2.60 and 128.53 μmol/h g, respectively. In the three-electrode electrochemical cell with 1 M Na₂SO₄ electrolyte and zero-bias, the photocurrent density of CuCoO₂ based photocathode reached to 20 μA/cm². These findings prove that CuCoO₂ has obvious advantages and great potential as a visible-light-driven photocatalyst.