TiO2/CuS heterostructure nanowire array photoanodes toward water oxidation: The role of CuS

Photoelectrochemical (PEC) water splitting represents a very attractive approach for the production of clean hydrogen by converting solar energy into chemical energy. However, their performance is limited by poor charge carrier separation and transportation. In this work, TiO2/CuS heterostructure nanowire array photoanodes were fabricated by decorating CuS nanoclusters on TiO2 nanowire arrays grown on conductive substrate via a successive ionic layer adsorption and reaction (SILAR) method. Results indicate that the CuS content increases with repeating the SILAR procedure. The PEC performance of the TiO2 nanowire array photoanodes is enhanced after loading CuS nanoclusters, and the TiO2/CuS-5 (i.e., repeating the SILAR process for 5 times) sample exhibits the highest photocurrent density. The enhancement of PEC activity is attributed to increased light absorption and efficient charge separation with an optimum CuS coverage on the TiO2 nanowire arrays. Importantly, further analysis reveals a reduction of partial CuS to Cu2S during the PEC process, indicating that the CuS nanoclusters are mainly acting as co-catalyst to transfer photogenerated electrons.