Photoelectrochemistry of p-type Cu2O semiconductor electrode in ionic liquid

We investigated the photoelectrochemical characteristics and photo-stability Of Cu2O layered on a copper plate using a hydrophobic ionic liquid. Our findings revealed that Cu2O is stable under white light irradiation, provided water is removed from the electrolyte. Methyl viologen derivative, a well-established electron acceptor, was introduced to the ionic liquid electrolyte, allowing the photo-induced electron transfer reaction at the Cu2O/electrolyte interface to be characterized. The methyl viologen derivative exhibited two distinct redox reactions at -0.56 V and -0.98 V vs. Ag/AgCl, clearly indicating that no dimer formation or co-proportionation reaction occurred. The excessive photocurrents being continuously generated resulted from a viable photo-induced electron transfer reaction from the Cu2O to the acceptor. However, in contrast, the reduction of the Cu2O by water in the aqueous solution causes this electron transfer to be inhibited. We further demonstrate that these findings are vital to understanding the role of the Cu2O and its photoelectrochemical applications.