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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, Ti3C2Tx 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 Ti3C2Tx MXene for self-powered PEC-type photodetector, HER, and vapor sensor applications. The suitable characteristics of Ti3C2Tx make it an appropriate substrate to accommodate Se atoms. The well-designed Se-doped Ti3C2 heterojunction including some TiO2 cuboids could exhibit unprecedented photoresponsivity (up to 90 mA W-1) and detectivity (up to 2.0×108 cm Hz1/2 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 Ti3C2Tx 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.

The exploitation of two-dimensional (2D) vanadium carbide (V2CTx, denoted as V2C) in electrocatalytic hydrogen evolution reaction (HER) and nitrogen reduction reaction (NRR) is still in the stage of theoretical study...

As a fascinating innovative class of effective catalysts for hydrogen evolution reaction (HER), transition-metal tellurides have emerged as attractive materials, but they are still suffering from their intrinsic activity for practical applications. Defect engineering constitutes a promising strategy to optimize the electronic configuration of the catalyst and further improve the HER activity. Herein, we present the successful fabrication of PdTe2-based catalysts with three different types of vacancies (d-PdTe x ), including single Pd, Te defect site, and double Te defect sites, by using a two-step method. The obtained d-PdTe x demonstrated a remarkable HER activity with an overpotential of 76 mV at 10 mA cm–2 without iR compensation, which is far lower than that of bulk PdTe2 (259 mV). The procedure followed in this work may be extended to generate defect sites in a range of different two-dimensional materials, thus further expanding their potential application fields.

oxidation reaction. In addition, an alteration of the active adsorption sites due to dilution of the catalytically active material may also take place when bimetallic catalysts are employed. Bismuth has already received interest as a Pt-modifier for electrocatalytic use. In this way, the noble metal quantity (and thus the overall cost) can be reduced, while the catalytic activity can be maintained (or even improved) by replacing a certain Pt amount with a less expensive metal. Bi may also modify the electronic structure of the Pt by lowering its d-band center. [1] Pt-Bi has been reported to be CO tolerant and it has exhibited higher catalytic performance for several oxidation reactions such as methanol, glycerol, ethylene glycol, and ethanol. The lower poisoning of Pt-Bi catalysts with CO has been proposed to be a determinant factor for the increase in catalytic activity of such materials. [2] Another example of an electrochemical reaction in which a bimetallic system can perform better than its monometallic counterpart is the electro-oxidation of formic acid. Pt-Bi showed a more negative onset potential and higher current density than monometallic Pt, together with the above-mentioned high tolerance to CO. [3] For the Pt-Bi alloy system, the PtBi 2 composition possesses a layered hexagonal crystal structure and has been suggested to behave as a 3D topological semimetal with very high magnetoresistance and unique electronic structures. A good comprehension of the electronic structure of PtBi 2 is required to properly assign the actual origin of its anomalous transport properties. [4] Pt-Bi bimetallic structures have found applications in thermoelectronics and batteries. Pt-Bi 2 O 3 has been shown to facilitate the photolysis of water, while single Pt or Bi 2 O 3 were unable to catalyze such reactions on their own. Pt-Bi/AC (activated carbon) is a commercially available catalyst for electrocatalysis and selective oxidation reactions. It has been suggested that Bi causes a geometric blocking effect on Pt, thus decreasing the active site ensemble of Pt. These decreased sites will still permit certain desired chemical reactions to occur, but they will not be active for specific undesired side reactions. The electronic properties of Bi help to increase the electrocatalytic activity of Pt, inhibiting poison effects, thanks to its small electron effective mass, low carrier concentrations, and highly anisotropic Fermi surface. [5,6] Pt-Bi alloy may not be the most suitable electrocatalyst for the oxygen reduction reaction (ORR); [7] still, though Pt-Bi catalysts Compositional and morphological tuning of bismuth-based nanomaterials is crucial to improve and broaden the application of such structures in a range of electrocatalytic reactions. Nanostructures composed of Pt-Bi and Pd-Bi alloys in different elemental proportions and shapes are produced by solvothermal and hydrothermal chemical routes at moderate temperatures. The alloying of cost-effective bismuth with platinum is found to be much more efficient than that with...