Ordered Mesoporous Metastable α‐MoC_1−x with Enhanced Water Dissociation Capability for Boosting Alkaline Hydrogen Evolution Activity

Abstract

The sluggish reaction kinetics of the alkaline hydrogen evolution reaction (HER) remains an important challenge for water-alkali electrolyzers, which originates predominantly from the additional water dissociation step required for the alkaline HER. In this work, it is demonstrated theoretically and experimentally that metastable, face-centered-cubic α-MoC 1−x phase shows superior water dissociation capability and alkaline HER activity than stable, hexagonal-close-packed Mo 2 C phase. Next, high surface area ordered mesoporous α-MoC 1−x (MMC) is designed via a nanocasting method. In MMC structure, the α-MoC 1−x phase facilitates the water dissociation reaction, while the mesoporous structure with high surface area enables a high dispersion of metal NPs and efficient mass transport. As a result, Pt nanoparticles (NPs) supported on MMC (Pt/MMC) show substantially enhanced alkaline HER activity in terms of overpotentials, Tafel slopes, mass and specific activities, and exchange current densities, compared to commercial Pt/C and Pt NPs supported on particulate α-MoC 1−x or β-Mo 2 C. Notably, Pt/MMC shows very low Tafel slope of 30 mV dec -1 , which is the lowest value among the reported Pt-based alkaline HER catalysts, suggesting the critical role of MMC in enhancing the HER kinetics. The promotional effect of MMC support in the alkaline HER is further demonstrated with an Ir/MMC catalyst.

Advanced Ultrathin RuPdM (M = Ni, Co, Fe) Nanosheets Electrocatalyst Boosts Hydrogen Evolution

“…1,2 Hydrogen energy as a clean, renewable resource can effectively alleviate the above environmental and resource problems, so hydrogen energy research is extremely urgent. 3−7 In recent years, many novel routes for generating hydrogen have been developed, such as photolysis 8−11 or electrolysis 12−14 of water to produce hydrogen. Among these approaches, electrocatalysis by virtue of the convenience and nonpolluting gas emissions have won the favor of many researchers.…”

Hierarchical MoP Hollow Nanospheres Anchored on a N,P,S‐Doped Porous Carbon Matrix as Efficient Electrocatalysts for the Hydrogen Evolution Reaction

“…Furthermore, the HER kinetics have been disclosed by using the Tafel plots, as illustrated in Figure 5c.H ere, Pt/C exhibits the lowest Ta fel slope of 33 mV dec À1 ,s uggesting that the Tafel reactioni st he rate-limiting step. [12] By contract, the Tafel slope of hs-MoP/NPSC-0.3 is 87.2 mV dec À1 ,w hich is noticeably lower than those of other hs-MoP/NPSC counterparts, indicating a Volmer-Heyrovsky mechanism with the hydrogen desorption reactiona st he rate-determining step. [26,58] The smaller Ta fel slope suggests the faster HER rate with ad ecreasei no verpotential.…”

“…To tackle the aforementioned challenges, intensivee fforts have been dedicated to designing various optimized Pt-free electrocatalysts, such as transition metal sulfides, [9][10][11] carbides, [11][12][13][14][15][16] nitrides, [17,18] and phosphides. [19,21] In particular, amongt he variousp romising alternatives, molybdenum phosphide (MoP) exhibitsaprominenta dvantage owing to their similare lectronic structure to Pt-group metals.…”

Synergistic Coupling of a Molybdenum Carbide Nanosphere with Pt Nanoparticles for Enhanced Ammonia Electro-Oxidation Activity in Alkaline Media

“…nanoparticles and MoC 1-x . This has been proven byBaek et al who recently showed that MoC 1-x as a support and promoter enhances water dissociation capability in alkaline media62 which made Pt/ MoC 1-x superior in hydrogen evolution to Pt/C. The decrease in the half and peak potentials of Pt/DG-MoC as compared to Pt/C implies the close proximity of the DG-MoC substrate and Pt nanoparticles that favours a strong synergistic effect between the nanoparticles by generating new bifunctional active centers in addition to platinum surface.…”