Facile Synthesis of TiO2 Nanothorn-coated Cu2O Nanowires with Improved Stability and Performance for Photoelectrochemical Water Splitting

Copper(I) oxide (Cu2O) based photocathodes are promising in photoelectrochemical (PEC) water splitting due to their bandgap, natural abundance, and low cost. However, the stability issues have impeded their practical application. This study presents a solution through a novel photocathode, TiO2 nanothorns-coated Cu2O nanowires (TCNW), synthesized using simple wet chemical methods. TCNW outperformed pristine Cu2O nanowires (CNW), achieving a stable PEC current density of ~3.8mA∙cm-2 at 0V vs RHE, compared to ~1.9mA∙cm-2 of CNW. TCNW also displayed an H2 evolution rate of ~64.2 μmol∙cm-2∙h-1 with a 93.9% faradaic efficiency, whilst CNW reached only ~6.8 μmol∙cm-2∙h-1 and 37.3%. These improvements stem from the protective TiO2 nanothorn layer, which enhances light absorption (300~500nm) and improves charge separation and transfer by forming a p-n junction with Cu2O. This work underscores the importance of well-crafted surface p-n junctions and conformal protective layers in optimizing the efficiency and stability.