Conductivity controlling of Cu2O film photoelectrode for water splitting by a novel electrochemical approach - Differential potentiostatic deposition

Cuprous oxide (Cu₂O) is a kind of low-cost and promising material for water splitting to produce hydrogen (p-type Cu₂O) and oxygen (n-type Cu₂O). However, the reason of conductivity transforming from p-type to n-type for Cu₂O films during potentiostatic deposition is waiting to be revealed. In this work, a novel electrochemical technology, differential potentiostatic deposition (DPD), is developed by coupling a 3-electrode setup with a resistor connected in series with the counter electrode circuit through a potentiostat. By this approach, deposition current density is adjusted in a short period to simulate different stages in a traditional potentiostatic deposition (TPD). The result shows that semiconducting conductivity of Cu₂O film changes from p-type to n-type with time during a long-term TPD in basic CuSO₄ solution. Employing the DPD method, conductivity of Cu₂O film transforms from p-type to n-type with current density decreasing. Through characterizing thickness, composition and photoelectrochemical performance of Cu₂O films, the mechanism of semiconducting conductivity transformation for Cu₂O films is proposed. Besides, the results indicate that the DPD is an effective method to tune the conductivity of metal oxide photoelectrodes for water splitting.