Low-energy hydrogen ions enable efficient room-temperature and rapid plasma hydrogenation of TiO2 Nanorods for Enhanced Photoelectrochemical Activity

Hydrogenation is a promising technique to prepare black TiO2 (H-TiO2) for solar water splitting, however, there remain limitations such as severe preparation conditions and underexplored hydrogenation mechanisms to inefficient hydrogenation and poor photoelectrochemical (PEC) perfor-mance to be overcome for practical applications. Here, a room-temperature and rapid plasma hydrogenation (RRPH) strategy that realizes low-energy hydrogen ions of below 250 eV to fabricate H-TiO2 nanorods with controllable disordered shell, outperforming incumbent hydrogenations, is reported. The mechanisms of efficient RRPH and enhanced PEC activity are experimentally and theoretically unraveled. It is discovered that low-energy hydrogen ions with fast subsurface transport kinetics and shallow penetration depth fea-tures, enable them to directly penetrate TiO2 via unique multiple penetration pathways to form controllable disordered shell and suppress bulk defects, ultimately leading to improved PEC performance. Furthermore, the hydrogen-ation-property experiments reveal that the enhanced PEC activity is mainly ascribed to increasing band bending and bulk defect suppression, compared to reported H-TiO2, a superior photocurrent density of 2.55 mA cm-2 at 1.23 VRHE is achieved. These findings demonstrate a sustainable strategy which offers great promise of TiO2 and other oxides to achieve further-improved material properties for broad practical applications.