Design Strategies for Large Current Density Hydrogen Evolution Reaction

Dual Function of Hypo-d-electronic Transition Metals in the Brewer Intermetallic Phase for the Highly Efficient Electrocatalytic Hydrogen Evolution Reaction in Alkaline Electrolytes

Reported are the synthesis, material characterization, and electrocatalytic hydrogen evolution reaction (HER) in acid and alkaline electrolytes for the Brewer intermetallic phase, Nb₆Co₇ and Mo₆Co₇. It was realized that the overpotential at a current density of 10 mA/cm² (η₁₀) for Nb₆Co₇ (η₁₀ = 62 mV) and Mo₆Co₇ (η₁₀ = 143 mV) are both much lower than that of using a single Co metal (η₁₀ = 253 mV) in alkaline electrolytes. The enhancement of electrocatalytic HER activity of Nb₆Co₇ and Mo₆Co₇ can be attributed to the hypo-hyper-d-electronic interaction between Nb/Mo and Co elements. Based on the result of density functional theory calculation, alloying between Nb/Mo and Co elements will increase the antibonding state population of the Co-Co bond near the Fermi level (E_F), which induces the synergistic effect to influence the adsorption energy of the H atom (ΔG_H) on the surface of Nb₆Co₇ and Mo₆Co₇. Moreover, the role of the Nb element is not only a simple electron donor but is also an anchor position for the OH molecule (i.e., dual function) due to the bonding character of the Nb-Co bond near E_F. It can reduce the OH position effect as well as the activation energy for water dissociation, which rationalizes the high and robust HER performance of Nb₆Co₇ to that of commercial Pt/C (η₁₀ = 67 mV) in alkaline electrolytes.

Recent progress of electrochemical hydrogen evolution over 1T-MoS2 catalysts

Developing efficient and stable non-noble metal catalysts for the electrocatalytic hydrogen evolution reaction (HER) is of great significance. MoS₂ has become a promising alternative to replace Pt-based electrocatalysts due to its unique layered structure and adjustable electronic property. However, most of the reported 2H-MoS₂ materials are stable, but the catalytic activity is not very ideal. Therefore, a series of strategies such as phase modulation, element doping, defect engineering, and composite modification have been developed to improve the catalytic performance of MoS₂ in the HER. Among them, phase engineering of 2H-MoS₂ to 1T-MoS₂ is considered to be the most effective strategy for regulating electronic properties and increasing active sites. Hence, in this mini-review, the common phase modulation strategies, characterization methods, and application of 1T-MoS₂ in the HER were systematically summarized. In addition, some challenges and future directions are also proposed for the design of efficient and stable 1T-MoS₂ HER catalysts. We hope this mini-review will be helpful to researchers currently working in or about to enter the field.