TiO2 nanotube arrays-based photoelectrocatalyst: Tri-Doping engineering and carbon coating engineering boosting visible activity, and stable hydrogen evolution.

[Display omitted] • Using a promising one-step vacuum space confined with carbon-coated tri-doped reaction method. • A unique novel core/shell structure comprises C N S-TiO 2 nanotubes and N S carbon coating. • Stable nitrogen, carbon and sulfur doping, and cocatalyst have synergistic effects. • Under simulated sunlight and visible light conditions, the photocurrent exhibited an increase of 18.3 times and 32.8 times, respectively. • The photoelectrocatalyst was recyclable and had excellent water splitting performance. The integration of non-metallic doping and carbon coating for TiO 2 -based photoelectrocatalysts can be recognized as a promising strategy to enhance their hydrogen production performance. To this end, this study explored the carbon coating engineering to induce stable multi-element doping with an aim to develop high-performance TiO 2 nanotube array-based photoelectrocatalysts. The resulting structures consisted of carbon–nitrogen-sulfur-tri-doped TiO 2 nanotube arrays with a nitrogen-sulfur-codoped carbon coating (C N S-TNTA/N S C). The fabrication process involved a one-step, low-cost strategy of the carbon-coated tridoped reaction confined in vacuum space, utilizing polymer thiourea sealed in a controlled environment. Compared the photocurrent density of C N S-TNTA/N S C with pristine TNTA, the photocurrent enhancement of approximately 18.3-fold under simulated sunlight and a remarkable increase of 32.8-fold under simulated visible light conditions. The enhanced photocatalytic activity under visible light was ascribed to two factors: First, C, N, and S tri-doping and Ti3+ created a diverse array of impurity energy levels within the band gap, which synergistically narrowed the band gap and further enhanced response to the visible light range. Second, the presence of a carbon coating shell doped with N and S can greatly promote electron transfer and efficient electron-hole pair separation. This study could provide significant insights concerning the design of sophisticated photoanodes. [ABSTRACT FROM AUTHOR]