Magnetic and electronic properties of single-walled Mo2C nanotube: a first-principles study

Heterointerface manipulation in the architecture of Co-Mo2C@NC boosts water electrolysis

Heterostructures with tunable electronic properties have shown great potential in water electrolysis for the replacement of current benchmark precious metals. However, constructing heterostructures with sufficient interfaces to strengthen the synergistic effect of multiple species still remains a challenge due to phase separation. Herein, an efficient electrocatalyst composed of a nanosized cobalt/Mo2C heterostructure anchored on N-doped carbon (Co-Mo2C@NC) was achieved by in situ topotactic phase transformation. With the merits of high conductivity, hierarchical pores, and strong electronic interaction between Co and Mo2C, the Co-Mo2C@5NC-4 catalyst shows excellent activity with a low overpotential for the hydrogen evolution reaction (HER, 89 mV@10 mA cm-2 in alkaline medium; 143 mV@10 mA cm-2 in acidic medium) and oxygen evolution reaction (OER, 356 mV@10 mA cm-2 in alkaline medium), as well as high stability. Furthermore, this catalyst in an electrolyzer shows efficient activity for overall water splitting and long-term durability. Theoretical calculations reveal the optimized adsorption-desorption behaviour of hydrogen intermediates on the generated cobalt layered hydroxide (Co LDH)/Mo2C interfaces, resulting in boosting alkaline water electrolysis. This work proposes a new interface-engineering perspective for the construction of high-activity heterostructures for electrochemical conversion.

Adsorption and diffusion of magnesium on nitrogen-doped Mo2C monolayer

The Mg adsorption and diffusion behaviors on nitrogen-doped (N-doped) Mo₂C monolayer have been investigated by the first principles based on density functional theory (DFT). To investigate the effect of nitrogen concentration on adsorption energies, Mo₂C_1-xN_x (x=0.0625, 0.125, 0.1875, and 0.25) with four different nitrogen doping concentrations have been considered in the present work. The results show that N-doped Mo₂C is benefit for Mg adsorption. In particular, when the doping concentration reaches to 14.29%, the adsorption energies of Mg on Mo₂C_0.875N_0.125 are in the region between -1.639 and -1.517 eV, e.g., the adsorption energies of Mg on T_C1 and H₂ sites are -1.639 eV and -1.625 eV, which are decreased by 16.49% and 18.43% as compared with the pristine Mo₂C. The calculations on diffusion behaviors show that the Mg diffusing between two adjacent favored sites via a high-symmetry site along H₃-B-H₄ and H₁-B-H₁ paths possesses the barriers of 0.021 eV and 0.028 eV. Additionally, the partial density of states (PDOS) reveals the interaction between Mg and Mo₂C_0.875N_0.125, and indicates that nitrogen doping causes the PDOS peaks transfer to a lower energy level, which is benefit for the bonding between Mg and Mo₂C_0.875N_0.125. These results suggest that the adsorption and diffusion behaviors of Mg have been enhanced by nitrogen doping.

Sustainable hydrogen production by molybdenum carbide-based efficient photocatalysts: From properties to mechanism

Hydrogen is considered to be a promising energy carrier to solve the issue of energy crisis. Molybdenum carbide (Mo_xC) is the typical material, which has similar properties of Pt and thought to be an attractive alternative to noble metals for H₂ evolution. The study of Mo_xC as alternative catalyst for H₂ production is almost focused on electrocatalytic field, while the application of Mo_xC as a co-catalyst in photocatalytic H₂ evolution has received in-depth research in recent years. Particularly, Mo_xC exhibits significant enhancement in the H₂ production performance of semiconductors under visible light irradiation. However, a review discussing Mo_xC serving as a co-catalysts in the photocatalytic H₂ evolution is still absent. Herein, the recent progress of Mo_xC on photocatalytic H₂ evolution is reviewed. Firstly, the preparation methods including chemical vapor deposition, temperature programming, and organic-inorganic hybridization are detailly summarized. Then, the fundamental structure, electronic properties, and specific conductance of Mo_xC are illustrated to illuminate the advantages of Mo_xC as a co-catalyst for H₂ evolution. Furthermore, the different heterojunctions formed between Mo_xC and other semiconductors for enhancing the photocatalytic performance are emphasized. Finally, perspectives regarding the current challenges and the future research directions on the improvement of catalytic performance of Mo_xC-based photocatalysts are also presented.