Hydrogen energy is a high-efficiency and clean energy, but the problem of storage still prevents its extensive use. Large-surface-area, two-dimensional (2D) layered materials have an advantage in hydrogen storage applications. Monolayer MoS₂ is a typical 2D material that has been widely studied recently. And the 1T′ phase of MoS₂ is a focus especially for studies concerning hydrogen. Here, first-principles calculations are carried out to investigate the adsorption behaviors of hydrogen molecules on 1T′ MoS₂. Comparing with other MoS₂-based materials, such as doped or decorated 2H-MoS₂, 1T′ MoS₂ has even better performance in hydrogen adsorption, and its preparation is easier. In multiple hydrogen molecule adsorption, the material shows good stability and appropriate adsorption energy while adsorbing hydrogen molecules. With the researches in this paper, the connection between the adsorption energy and hydrogen mass fraction was set up. This can provide a reference for further studies on hydrogen storage applications.

Two-dimensional transition metal dichalcogenides (2D TMDs), such as WS₂, are considered to have the potential for high-performance gas sensors. It is a pity that the interaction between gases and pristine 2D WS₂ as the sensitive element is too weak so that the sensor response is difficult to detect. Herein, the sensing capabilities of Al- and P-doped WS₂ to NO, NO₂, and SO₂ were evaluated. Especially, we considered selectivity to target gases and dopant concentration. Molecular models of the adsorption systems were constructed, and density functional theory (DFT) was used to explore the adsorption behaviors of these gases from the perspective of binding energy, band structure, and density of states (DOS). The results suggested that doping atoms could increase the adsorption strength between gas molecules and substrate. Besides, the sensitivity of P-doped WS₂ to NO and NO₂ was hardly affected by CO₂ or H₂O. The sensitivity of Al-doped WS₂ to NO₂ and SO₂ was also hard to be affected by CO₂ or H₂O. For NO detection, the WS₂ with 7.4% dopant concentration had better sensitive properties than that with a 3.7% dopant concentration. While for SO₂, the result was just the opposite. This work provided a comprehensive reference for choosing appropriate dopants (concentration) into 2D materials for sensing noxious gases.

Hydrogen-air proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs) are excellent fuel cells with high limits of energy density. However, the low carbon monoxide (CO) tolerance of the Pt electrode catalyst in hydrogen-air PEMFCs and methanol permanent in DMFCs greatly hindered their extensive use. Applying polybenzimidazole (PBI) membranes can avoid these problems. The high thermal stability allows PBI membranes to work at elevated temperatures when the CO tolerance can be significantly improved; the excellent methanol resistance also makes it suitable for DMFCs. However, the poor proton conductivity of pristine PBI makes it hard to be directly applied in fuel cells. In the past decades, researchers have made great efforts to promote the proton conductivity of PBI membranes, and various effective modification methods have been proposed. To provide engineers and researchers with a basis to further promote the properties of fuel cells with PBI membranes, this paper reviews critical researches on the modification of PBI membranes in both hydrogen-air PEMFCs and DMFCs aiming at promoting the proton conductivity. The modification methods have been classified and the obtained properties have been included. A guide for designing modifications on PBI membranes for high-performance fuel cells is provided.

The potential of modified MoS₂-based materials in oxygen reduction reaction (ORR) was evaluated by DFT calculations.