Ultrafine nano 1T-MoS₂ monolayers with NiO_x as dual co-catalysts over TiO₂ photoharvester for efficient photocatalytic hydrogen evolution

Molybdenum disulfide (MoS₂) of 1 T phase was found to potentially replace Pt as efficient co-catalyst for the hydrogen evolution reaction (HER). Herein, an ultrafine nano 1 T-MoS₂ monolayer of around 10 nm was successfully synthesized and showed a high electrocatalytic HER activity with low overpotential of 78 mV at 10 mA cm⁻². When the 1 T-MoS₂ is loaded onto P25 TiO₂, its ultrafine size dramatically promotes the superior interface bonding with TiO₂ and a high photocatalytic HER activity of 300.3 μmol h⁻¹ is obtained. Furthermore, a strategy by introducing NiO_x co-catalyst into the 1 T-MoS₂/P25 to fabricate a dual co-catalyst composite 1 T-MoS₂/P25/NiO_x significantly improves the photocatalytic HER activity to 1629.1 μmol h^-1 which is very close to Pt/P25 of 2196.8 μmol h^-1. The close interface-bonding between the nanosized 1 T-MoS₂ monolayer and P25 along with the assistance of NiO_x results in the superior photocatalytic HER activity by the enhanced separation and transfer of the photogenerated electrons and holes.