Surface densification strategy assisted efficient Cu₂O heterojunction photocathode for solar water splitting

Photoelectrochemical (PEC) water splitting based on abundant and promising Cu₂O photocathode offers new possibilities for energy and climate crisis mitigation. Magnetron sputtering (MS) is a simple, reliable, and commercially proven scalable technique for fabricating Cu₂O with excellent electronic properties. However, the small nanograin and cracking nature of the Cu₂O nanofilm deposited by MS limited the subsequent heterojunction fabrication indispensable for capable devices. In this work, we have developed a simple surface densification strategy using another facile electrochemical deposition method to address this critical issue. The modified Cu₂O-based photocathode presented a photocurrent density of 4 mA/cm² at H₂ evolution potential, which is 10 times higher than the unmodified device and 1.6 times that of the conventional device based on the electrochemical deposition method. Furthermore, we implemented comprehensive photoelectric characterization and energy band simulations to gain insight into the carrier dynamics in Cu₂O, revealing the efficient separation of carriers in the modified specimen and the factor that limits the device performance. This paper provides a novel and simple approach to engineer efficient Cu₂O photocathodes for PEC H₂ generation based on the commercial MS technique.