The Tune Effect of Surface Pt/Mo Ratio on the Stability and Morphology of α-MoC surfaces

Gong, Juhui; Sun, Ruiqin; Cui, Linxia; Cao, Cheng; Shi, Ke; Zhang, Mingyuan; Gao, Rui; Hao, Haigang

doi:10.1016/j.surfin.2020.100831

Cited by 3 publications

(3 citation statements)

References 45 publications

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“…The PMA precursor was impregnated into the mesopores of the KIT-6 template and carburized using CH 4 /H 2 /Ar mixture gas as a carbon source. In optimized synthesis conditions, we used a mixture gas with a high CH 4 concentration (CH 4 :H 2 = 2:1, vol %) and a rapid ramping rate (10 °C min –1 ) to induce higher μ C , which can consequently facilitate the formation of the metastable α-MoC 1– x phase. , The subsequent etching of KIT-6 produced MMC, and its postsynthetic thermal annealing under H 2 gave rise to MMC-H 2 with a significantly decreased thickness of the carbon overlayer.…”

Section: Resultsmentioning

confidence: 99%

“…The α-MoC 1– x phase molybdenum carbides are, however, only attained in a limited range of synthetic parameter windows with temperature-programmed reaction-based methods. In addition to these experimental efforts, recent theoretical studies , revealed that the phase stability of the metastable fcc α-MoC 1– x crystal can be obtained as the carbon chemical potential (μ C , μ C = μ CH4 – 2μ H 2 for the dissociation of CH 4 into C and 2H 2 ) increases and the particle size of molybdenum carbide decreases.…”

Section: Introductionmentioning

confidence: 99%

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Metastable Phase-Controlled Synthesis of Mesoporous Molybdenum Carbides for Efficient Alkaline Hydrogen Evolution

2022

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Transition metal carbides (TMCs) have shown great promise as nonprecious metal electrocatalysts for electrochemical energy conversion reactions owing to their Pt-like catalytic activity. The major challenges in the synthesis of TMCs include the selective formation of a catalytically active phase, enlargement of the catalytically active surface area, and control of the carbonaceous overlayer, all of which collectively influence their catalytic reactivity. Herein, we present a systematic study on the catalytically active metastable phase-selective synthesis of mesoporous molybdenum carbides with controlled carbon overlayer thickness for efficient alkaline hydrogen evolution reaction (HER) electrocatalysis. The synthesis of molybdenum carbides was explored by controlling the types of Mo and C precursors and carburization conditions and the use of a mesoporous silica template. The choice of the Mo precursor and the nanospace-confined carburization were identified as critical factors for the formation of mesoporous molybdenum carbides of the metastable α-MoC1–x phase (MMC) with a large catalytically active surface area. The thickness of the carbon overlayer on the surfaces of the molybdenum carbides increased proportionally with the carburization temperature and decreased substantially with H2 post annealing. Among the prepared catalysts, the H2-annealed MMC (MMC-H2) exhibited the highest alkaline HER activity and reaction kinetics, which is one of the best among the meal carbide alkaline HER catalysts reported so far and compared favorably with a commercial Pt/C catalyst. The MMC-H2 also demonstrated superior durability and stability as compared to MMC and Pt/C catalysts.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Metastable Phase-Controlled Synthesis of Mesoporous Molybdenum Carbides for Efficient Alkaline Hydrogen Evolution

2022

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“…Moreover, all surface models in this paper are shown in Figures S1–S4 for the sake of clarity. The comparison of surface energy can reflect the stability of the laminated structure; to study the influence of defects and disorder on the stability of laminates, we first compared the energies of all of these surfaces. One should notice that the defect formation energy must be taken into consideration while comparing the energies.…”

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confidence: 99%

Interplay between Defects and Short-Range Disorder Manipulating the Oxygen Evolution Reaction on a Layered Double Hydroxide Electrocatalyst

Li,

Yang,

Gao

et al. 2024

J. Phys. Chem. Lett.

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Improving the efficiency of the oxygen evolution reaction (OER) is crucial for advancing sustainable and environmentally friendly hydrogen energy. Layered double hydroxides (LDHs) have emerged as promising electrocatalysts for the OER. However, a thorough understanding of the impact of structural disorder and defects on the catalytic activity of LDHs remains limited. In this work, a series of NiAl-LDH models are systematically constructed, and their OER performance is rigorously screened through theoretical density functional theory. The acquired results unequivocally reveal that the energy increase induced by structural disorder is effectively counteracted at the defect surface, indicating the coexistence of defects and disorder. Notably, it is ascertained that the simultaneous presence of defects and disorder synergistically augments the catalytic activity of LDHs in the context of the OER. These theoretical findings offer valuable insights into the design of highly efficient OER catalysts while also shedding light on the efficacy of LDH electrocatalysts.

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A Review of Preparation Strategies for α-MoC1–x Catalysts

Zanet

Kondrat

2022

Johnson Matthey Technology Review

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Transition metal carbides are attracting growing attention as robust and affordable alternative heterogeneous catalysts to platinum group metals, for a host of contemporary and established hydrogenation, dehydrogenation, and isomerisation reactions. In particular, the metastable α-MoC1-x phase has been shown to exhibit interesting catalytic properties for low temperature processes reliant on O-H and C-H bond activation. While demonstrating exciting catalytic properties, a significant challenge exists in the application of metastable carbides, namely the challenging procedure for their preparation. In this review we will briefly discuss the properties and catalytic applications of α-MoC1-x, followed by a more detailed discussion on available synthesis methods and important parameters that influence carbide properties. Techniques are contrasted with properties of phase, surface area, morphology and Mo:C being considered. Further, we briefly relate these observations to experimental and theoretical studies of α-MoC1-x in catalytic applications. Synthetic strategies discussed are, the original temperature programmed ammonolysis followed by carburisation, alternative oxycarbide or hydrogen bronze precursor phases, heat treatment of moybdate-amide compounds and other low temperature synthetic routes. The importance of carbon removal and catalyst passivation in relation to surface and bulk properties are also discussed. Novel techniques that by-pass the apparent bottle neck of ammonolysis are reported, however a clear understanding of intermediate phases is required to be able to fully apply these techniques. Pragmatically, the scaled application of these techniques requires the pre-pyrolysis wet chemistry to be simple and scalable. Further, there is a clear opportunity to correlate observed morphologies/phases and catalytic properties with findings from computational theoretical studies. Detailed characterisation throughout the synthetic process is essential and will undoubtedly provide fundamental insights that can be used for the controllable and scalable synthesis of metastable α-MoC1-x.

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The Tune Effect of Surface Pt/Mo Ratio on the Stability and Morphology of α-MoC surfaces

Cited by 3 publications

References 45 publications

Metastable Phase-Controlled Synthesis of Mesoporous Molybdenum Carbides for Efficient Alkaline Hydrogen Evolution

Metastable Phase-Controlled Synthesis of Mesoporous Molybdenum Carbides for Efficient Alkaline Hydrogen Evolution

Interplay between Defects and Short-Range Disorder Manipulating the Oxygen Evolution Reaction on a Layered Double Hydroxide Electrocatalyst

A Review of Preparation Strategies for α-MoC1–x Catalysts

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