Ti3C2T x MXene anchoring semi-metallic selenium atoms: self-powered photoelectrochemical-type photodetector, hydrogen evolution, and gas-sensing applications

Abstract MXenes have demonstrated substantial promise as photocatalysts and electrocatalysts for a variety of applications such as self-powered photoelectrochemical (PEC)-type photodetector, hydrogen evolution reaction (HER), and vapor sensing applications. However, their mechanism is still poorly figured out. Currently, Ti 3 C 2 T x MXene suffers from low photoresponsivity, high overpotential, and low sensitivity in such important applications. In order to develop catalytic activity and performances of those devices, modifications must be made to the structure of MXenes to enhance the separation of photogenerated charges, rate of the H + /e − couplings, and surface-active sites. These manipulations of MXenes heavily depend on understanding the mechanism of devices, appropriate modification elements, and the method of modification. This study for the first time reveals a facile solid-state annealing strategy for doping semi-metallic selenium (Se) atoms on Ti 3 C 2 T x MXene for self-powered PEC-type photodetector, HER, and vapor sensor applications. The suitable characteristics of Ti 3 C 2 T x make it an appropriate substrate to accommodate Se atoms. The well-designed Se-doped Ti 3 C 2 heterojunction including some TiO 2 cuboids could exhibit unprecedented photoresponsivity (up to 90 mA W −1 ) and detectivity (up to 2.0 × 10 8 cm Hz 1/2 W −1 ) for 420 nm light, HER (−0.7 V at 10 mA cm −2 ), and gas sensitivity (Z′ = 347 Ω and Z′′ = 150 Ω, for ethanol) in comparison with the pristine Ti 3 C 2 T x nanosheets. The acquired promising results can be promoted with some other elements and also be examined in other electrolytes. Then, bring inspiration to the applications involving charge transfer, H + /e − couplings, and surface-active sites.