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. (c) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.