NiOOH-Mediated Electron Injection into Ti3C2Fx to Weaken Ti-H Bond for Accelerated Photocatalytic Hydrogen Production

Abstract

Ti3C2 MXene (Ti3C2Tx), a two-dimensional transition metal carbide, is widely regarded as a highly promising cocatalyst for photocatalytic hydrogen evolution due to its high electrical conductivity and tunable surface terminations. However, the excessively strong Ti-H bond strength in conventional Ti3C2 MXene leads to unfavorable hydrogen desorption kinetics, which is further exacerbated due to an overabundance of highly electronegative F-terminations on Ti3C2Tx from F-containing etchant (Ti3C2Fx). This study proposes constructing a NiOOH-Ti3C2Fx heterojunction to facilitate electron transfer from NiOOH to Ti3C2Fx for increasing Ti 3d antibonding orbital occupancy state. The NiOOH-Ti3C2Fx/CdS photocatalysts are prepared through a two-step process, including the initial formation of NiOOH on Ti3C2Fx by a precipitation reaction and the subsequent in-situ growth of CdS onto the NiOOH-Ti3C2Fx surface. Photocatalytic hydrogen evolution tests demonstrated that the NiOOH-Ti3C2Fx/CdS photocatalyst achieved a significantly enhanced hydrogen production rate of 2.42 mmol h -1 g -1 , representing 7.8 times and 4.94 times improvements over pristine CdS and Ti3C2Fx/CdS, respectively. DFT calculations and spectroscopic analyses reveal that the electron transfer from NiOOH to Ti3C2Fx increases Ti 3d antibonding orbital occupancy, thereby weakening the Ti-Hads bond. This study provides critical insights into modulating the hydrogen adsorption capacity at Ti sites for efficient solar fuel production.