Single‐crystal TiO 2 /SrTiO 3 core–shell heterostructured nanowire arrays for enhanced photoelectrochemical performance

Vertically aligned TiO 2 /SrTiO 3 core–shell heterostructured nanowire arrays with different shell thicknesses (5–40 nm) were fabricated on fluorine‐doped tin oxide substrate via a hydrothermal process. Microstructural characterization demonstrated that the TiO 2 nanowires were uniformly coated by the single‐crystal SrTiO 3 shell, where continuous and large‐area interface could be clearly observed. By this means, significantly enhanced photoelectrochemical water splitting properties (0.78 mA·cm −2 at 1.23 V vs. RHE) were successfully realized in well‐designed sample (with a shell thickness of 5–10 nm) compared with those of pristine TiO 2 (0.38 mA·cm −2 at 1.23 V vs. RHE). The improvement of photoelectrochemical properties was attributed to the improved charge injection and charge separation, which are calculated by the results of water oxidation and sulfite oxidation measurements. Based on these results, a mechanism was proposed that SrTiO 3 shell acted as an electron–hole separation layer to improve the photocurrent density. On the other hand, the sample with an over‐thick SrTiO 3 shell (20–40 nm) exhibited slightly reduced photoelectrochemical properties (0.66 mA·cm −2 ), which could be explained by the increase of the recombination rate in the thicker SrTiO 3 shell. This work provided a facile strategy to improve and modulate the photoelectrochemical performance of heterostructured photoanodes.