Electrodeposition of Cuprous Oxide on a Free-Standing Porous Cu Framework for Photoelectrochemical Water Splitting

The use of hydrogen as a chemical fuel is an attractive and promising method as an alternative sustainable green energy carrier. The combination of direct sunlight and semiconductor photoelectrodes in a photo-electrochemical (PEC) cell can generate hydrogen by splitting water molecules into H 2 and O 2 1 . Copper(I) oxide or Cuprous oxide (Cu 2 O) is a p-type semiconductor with a bandgap of ~2 eV which makes it suitable for solar visible light absorption and it possesses a suitable band position for water reduction to hydrogen in the PEC cell 2 . The focus here is to increase the surface area of Cu 2 O photocathode to improve the PEC water splitting performance. Using dynamic hydrogen-bubble assisted electrochemical deposition method, a highly porous Cu substrate was synthesized in an acid copper sulfate bath at current densities above -1 A/cm 2 . To obtain a free-standing porous copper framework the structure must be reinforced at a lower current density using the same acidic bath and was separated from the substrate via ultrasonication The Cu 2 O crystal was then deposited on the free-standing porous Cu framework from an alkaline copper bath. The photoelectrochemical analysis of Cu 2 O was performed using a solar simulator at 1.5 AM and it shows a significant improvement of the photocurrent in comparison to the planar sample. M. Grätzel, Nature , 414 , 338–344 (2001). A. Paracchino, V. Laporte, K. Sivula, M. Grätzel, and E. Thimsen, Nat. Mater. , 10 , 456–461 (2011). Figure 1