提升二维材料的电催化析氢和光催化析氢性能的策略

世界能源危机问题和环境问题日益突出,寻找低廉、易得且能够替代化石的清洁能源是目前研究的热点.氢气具有可再生性、安全、高能量密度、环境友好型等优点,因而成为替代化石燃料的首选.在众多途径中,电催化产氢和光催化产氢是目前应用较广且比较成熟的方法,其工艺过程简单、无污染,但由于效率较低或生产成本较高等因素,其大规模应用受到一...     

Nitrogen doped FeS2 nanoparticles for efficient and stable hydrogen evolution reaction

Performance breakthrough of electrocatalysts highly relies on the regulation of internal structures and electronic states.In present work,for the first time,we successfully synthesized nitrogen doped FeS₂ nanoparticles(N-FeS₂)as the electrocatalysts for hydrogen evolution reaction(HER).The band structure and electronic state of FeS₂ are modulated by a nitrogen doping strategy,as confirmed by X-ray photoelectron spectroscopy(XPS),X-ray absorption spectroscopy(XAS)and density functional theory(DFT)calculations.Owing to the band structure and electronic state regulation as well as the weakening of H-S interaction,the designed N-FeS₂ electrocatalyst exhibits superior catalytic performance with a low overpotential(~126 mV at 10 mA cm^-2)and excellent activity stability under alkaline conditions,which is substantially improved as compared with that of the pure FeS₂ counterpart.Our work demonstrates that the modulation of electron state and band structure of an electrocatalyst,which can provide a valuable guidance for designing excellent catalysts for hydrogen evolution reaction and beyond.     

Phase engineering two-dimensional nanostructures for electrocatalytic hydrogen evolution reaction

Hydrogen(H₂) is considered to be a promising substitute for fossil fuels. Two-dimensional(2D) nanomaterials have exhibited an efficient electrocatalytic capacity to catalyze hydrogen evolution reaction(HER).Particularly, phase engineering of 2D nanomaterials is opening a novel research direction to endow 2D nanostructures with fascinating properties for deep applications in catalyzing HER. In this review, we briefly summarize the research progress and present the current challenges on...     

Dopant-vacancy activated tetragonal transition metal selenide for hydrogen evolution electrocatalysis

Hydrogen production from water electrolysis using renewable electricity is a highly promising route to solve the energy crisis of human society. The tetragonal 3d-transition metal selenide with metallic feature has been discovered to efficiently catalyze the hydrogen evolution electrocatalysis; however, its performance is still unsatisfactory and further improvement is necessary. Herein, the hydrogen evolution reaction of the functional tetragonal 3d-transition metal selenide with the heteroatom-dopant as well as cationic vacancy is fully investigated by means of density functional theory calculations. Our results identify 53 promising candidates endowed with good activity due to the absolute free energy of hydrogen adsorption |∆G_H| ≤ 0.30 eV wherein 15 candidates with |∆G_H| ≤ 0.09 eV possess compelling performance in comparison with the benchmark Pt material. Interestingly, the functional CuSe systems account for 29 out of 53 candidates, being high attractive for experimental synthesis. According to the analysis of electronic structure, the enhanced performance stems from the upshift of the sp orbitals, which benefits for the improved affinity toward hydrogen capture. This work provides new direction and guidance for the design of novel electrocatalysts.     

Noble metal doped graphene nanocomposites and its study of photocatalytic hydrogen evolution

This work reports the deposition of platinum (Pt) nanoparticles on the surface of graphene nanosheet by a simple approach, using a microwave-assisted method. The photocatalytic activity has been investigated for hydrogen evolution. The hydrogen evolutions were attributed to graphene, due to its high photoelectron transport properties, and the Pt nanoparticles attached on the surface of graphene sheet, which act as reaction centers for H₂ evolution. The “as-prepared” composites were characterized by Brunauer Emmett Teller (BET) surface area measurement, X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). This work highlights the potential application of graphene-based materials in the field of energy conversion.     

Ultrafine molybdenum carbide nanoparticles supported on nitrogen doped carbon nanosheets for hydrogen evolution reaction

Nitrogen doped carbon nanosheets supported molybdenum carbides nanoparticles (Mo_xC/NCS) have been synthesized by tuning the mass ratio of melamine and ammonia molybdate. The Mo₂C/NCS-10 exhibits superior electrocatalytic performance and stability for HER, which was attributed to N-doped carbon nanosheets, small particle size, mesoporous structure, and large electrochemical active surface area.     

Tetrazole-functionalized two-dimensional covalent organic frameworks coordinated with metal ions for electrocatalytic oxygen evolution reaction

The search for functionalized covalent organic framework (COF) materials is significant on account of their great promise for frontline applications in various fields. Herein, a novel and convenient tactic is developed to design and fabricate the tetrazole-functionalized COF materials with abundant nitrogen atoms, which can provide active sites, facilitating the incorporation of COFs with metal ions. In particular, a β-ketoenamine-linked COF named COF-TpDb is selected as precursor for postsynthetic modification to introduce the tetrazole moieties to coordinate with metal ions cobalt (Co²⁺) and palladium (Pd²⁺), giving two functional metal-coordinated COFs complexes COF-TpDb-TZ-Co and COF-TpDb-TZ-Pd. The resultant COF-TpDb-TZ-Co displays a higher oxygen evolution reaction activity with a lower overpotential of 390 mV at a current density of 10 mA cm^?2, which is much enhanced compared with COF-TpDb-TZ. The tactic for the fabrication of tetrazole-functionalized COFs with abundant nitrogen atoms implements rational design for the construction of functional COFs and expands the promising application of metal-coordinated COF materials in electrocatalysis.     

Electrochemical sulfidation of WS2 nanoarrays: Strong dependence of hydrogen evolution activity on transition metal sulfide surface composition

The activity of transition metal sulfides for the hydrogen evolution reaction (HER) can be increased by sulfur-enrichment of active metal-sulfide sites. In this report, we investigate the electrochemical sulfidation of atmospherically aged WS₂ nanoarrays with respect to enhancing HER activity. In contrast to MoS₂, it is found that sulfidation diminishes HER activity. Electrochemical and XPS experiments suggest the involvement of insoluble tungsten oxides in the altered HER and electron transfer properties. This demonstrates the strong dependence of the transition metal dichalcogenide (TMD) composition with the successful sulfur incorporation and subsequent HER activity.     

N-doped Mo2C nanoblock for efficient hydrogen evolution reaction

Journal of Solid State Electrochemistry - The development of Pt-free electrocatalysts for hydrogen evolution reaction (HER) is still desired in water-splitting as a clean energy. As a highly...     

Susceptibility of FeS2 hydrogen evolution performance to sulfide poisoning

The imminent depletion of fossil fuels raises concern over the need for next-generation clean energy. Of numerous alternatives, electrochemical water splitting is a promising method to store energy in the form of hydrogen. In order to benefit from this system, technological advancement in the development of affordable and efficient electrocatalysts for hydrogen evolution reaction is necessary. Transition-metal electrocatalysts composing of earth-abundant elements, specifically natural FeS₂, has demonstrated excellent performance for hydrogen evolution reaction. However, previous studies on platinum surfaces highlighted the detrimental effect toward hydrogen evolution performance upon poisoning of the active sites. In this work, we examine the susceptibility of natural FeS₂ toward sulfide poisoning. Our findings showed that the degradation effect from the introduction of sulfide to natural FeS₂ was not as severe as that observed on platinum. The overpotential (at a current density of 10 mA/cm²) for natural FeS₂ and platinum increased by approximately 20 and 110 mV, respectively.     

NiO改性C3N5光催化剂析氢性能研究（英文）

近年来,新型光催化剂氮化碳（C₃N₅）因其优异的光捕获性能和独特的二维结构备受关注。然而,较高的电子-空穴复合率严重影响其光催化性能。本研究采用水热法成功合成了氧化镍（NiO）改性的C₃N₅ p-n异质结纳米光催化剂。结果表明,9-Ni/C₃N₅纳米光催化剂在可见光照射下表现出优异的析氢性能,其析氢速率可高达357μmol/（g·h）,是纯C₃N₅的107倍。这主要归因于9-Ni/C₃N₅纳米光催化剂形成p-n异质结,有效促进了光生电子-空穴对的分离,从而提高了析氢效率。     

Enhancement of hydrogen evolution activities of low-cost transition metal electrocatalysts in near-neutral strongly buffered aerobic media

The advantages of hydrogen evolution reaction (HER) in strongly buffered neutral pH are manifold including enhanced stability of the electrocatalysts, oxygen tolerance, safer and environmental friendly devices, etc., yet, not much research effort has been devoted on the subject. HER activities of several low-cost electrocatalysts like Mo₂C, MoS₂, CoSe₂ and NiSe₂ have been studied in sodium phosphate buffer solution of pH 5. An optimal buffer concentration of 1.75 M was observed for the electrocatalysts. Compared to un-buffered electrolyte, a reduction of about 100 mV in the onset overpotential has been achieved. The electrocatalysts are highly oxygen tolerant with more than 90% HER selectivities. Furthermore, electrochemical surface area of Mo₂C was evaluated by capacitance and surface oxidation methods to obtain an insight on the specific adsorption of buffer electrolytes.     

Thermoelectric properties of two-dimensional ternary transition metal nitrides HfNF

The exceptional electron transfer properties and low thermal conductivity of two-dimensional layered materials render them a promising choice for thermoelectric applications. In this study, we explore the stability, electronic properties, and thermoelectric characteristics of materials composed of two-dimensionally layered transition metal nitride HfNF. Our research findings show that the structure of HfNF is stable and exhibits the properties of a direct bandgap semiconductor. Furthermore, we employ the Boltzmann transport theory and Slack model to investigate the thermoelectric properties of HfNF within the temperature range of 300 to 900 K. The HfNF materials exhibit relatively large thermoelectric dominance values ( $$ values), with the $$-type HfNF demonstrating a maximum $$ value of 1.46. Furthermore, utilizing the quasi-harmonic Debye model, thermodynamic properties such as heat capacity, coefficient of thermal expansion, and bulk modulus within the 6 GPa and 600 K range are estimated. Based on these calculations, it is predicted that two-dimensional HfNF materials will serve as promising new materials for thermoelectric applications spanning from 300 to 900 K.     

Single-atom Pt promoted Mo2C for electrochemical hydrogen evolution reaction

Hydrogen generation from electrochemical water splitting powered by renewable energy is important to the sustainable society,but the prohibitive cost of current...     

CoS2 nanowires supported graphdiyne for highly efficient hydrogen evolution reaction

Transition metal sulfides are an important category for hydrogen evolution reaction(HER).However,only few edge unsaturated sulfurs functionalize as catalytic si...     

A theoretical evaluation of possible transition metal electro-catalysts for N2 reduction

Theoretical studies of the possibility of forming ammonia electrochemically at ambient temperature and pressure are presented. Density functional theory calculations were used in combination with the computational standard hydrogen electrode to calculate the free energy profile for the reduction of N(2) admolecules and N adatoms on several close-packed and stepped transition metal surfaces in contact with an acidic electrolyte. Trends in the catalytic activity were calculated for a range of transition metal surfaces and applied potentials under the assumption that the activation energy barrier scales with the free energy difference in each elementary step. The most active surfaces, on top of the volcano diagrams, are Mo, Fe, Rh, and Ru, but hydrogen gas formation will be a competing reaction reducing the faradaic efficiency for ammonia production. Since the early transition metal surfaces such as Sc, Y, Ti, and Zr bind N-adatoms more strongly than H-adatoms, a significant production of ammonia compared with hydrogen gas can be expected on those metal electrodes when a bias of -1 V to -1.5 V vs. SHE is applied. Defect-free surfaces of the early transition metals are catalytically more active than their stepped counterparts.     

Ionic-liquid-mediated active-site control of MoS2 for the electrocatalytic hydrogen evolution reaction

The layered crystal MoS(2) has been proposed as an alternative to noble metals as the electrocatalyst for the hydrogen evolution reaction (HER). However, the activity of this catalyst is limited by the number of available edge sites. It was previously shown that, by using an imidazolium ionic liquid as synthesis medium, nanometre-size crystal layers of MoS(2) can be prepared which exhibit a very high number of active edge sites as well as a de-layered morphology, both of which contribute to HER electrocatalytic activity. Herein, it is examined how to control these features synthetically by using a range of ionic liquids as synthesis media. Non-coordinating ILs with a planar heterocyclic cation produced MoS(2) with the de-layered morphology, which was subsequently shown to be highly advantageous for HER electrocatalytic activity. The results furthermore suggest that the crystallinity, and in turn the catalytic activity, of the MoS(2) layers can be improved by employing an IL with specific solvation properties. These results provide the basis for a synthetic strategy for increasing the HER electrocatalytic activity of MoS(2) by tuning its crystal properties, and thus improving its potential for use in hydrogen production technologies.     

Catalytic activity of transition metal silicides in hydrogen oxidation

The catalytic activity of transition metal silicides in H₂ oxidation is much higher compared to metal-like carbides, which can be due to the lower electronegativity of silicon compared to carbon.

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Ni-W-TiO2复合电极在碱性介质中的析氢电催化性能

具有较高的析氢电催化活性的镍基多元合金材料已广为报道。近年来通过复合电沉积技术在电极中掺入RuO2、ZrO2、WC等非溶性固体微粒制备的复合功能电极材料用于析氢方面的研究已有报道,这些复合电极对析氢反应都有明显的催化作用。但是用电沉积的方法在电极中掺入TiO2制备的复合功能材料的研究还未见报道,本文研究了Ni-W-TiO2复合电极的制备、形貌结构以及在碱性介质中的析氢电催化活性和电化学稳定性。     

The nature of synergistic effects in transition metal oxides/in-situ intermediate-hydroxides for enhanced oxygen evolution reaction

Oxygen evolution reaction is highly important for hydrogen production via water splitting but requires ～0.22 V onset overpotential, resulting in at least 15% extra energy consumption even utilized with the benchmark hetero-doped transition-metal hydroxide catalysts. The lack of fundamental understanding on catalyst behaviour and on synergistic mechanisms limit the breakthrough for material design. Here, we systematically summarise a variety of investigations and arguments on the mechanism from the microscale (optimal octahedral intermediate with six M?O coordination) to atomic scale (the active site behaviour). The electron–orbital scale (e_g) is further described for the intrinsic OER activity. The synergistic effect may also lead to a short-cut pathway of lattice-oxygen-mediated mechanism to achieve a smaller overpotential. This review provides a theoretical reference for the design of advanced catalysts.