Electrochemical hydrogen evolution reaction (HER) from water splitting driven by renewable energy is considered a promising method for large-scale hydrogen production, and as an alternative to noble-metal electrocatalysts, molybdenum carbide (Mo2C) has exhibited effective HER performance. However, the strong bonding strength of intermediate adsorbed H (Hads) with Mo active site slows down the HER kinetics of Mo2C. Herein, using phase-transition strategy, hexagonal β-Mo2C could be easily transferred to cubic δ-Mo2C through electron injection triggered by tungsten (W) doping, and heterointerface-rich Mo2C-based composites, including β-Mo2C, δ-Mo2C, and MoO2, are presented. Experimental results and density functional theory calculations reveal that W doping mainly contributes to the phase-transition process, and the generated heterointerfaces are the dominant factor in inducing remarkable electron accumulation around Mo active sites, thus weakening the Mo─H coupling. Wherein, the β-Mo2C/MoO2 interface plays an important role in optimizing the electronic structure of Mo 3d orbital and hydrogen adsorption Gibbs free energy (ΔGH*), enabling these Mo2C-based composites to have excellent intrinsic catalytic activity like low overpotential (η10 = 99.8 mV), small Tafel slope (60.16 dec−1), and good stability in 1 m KOH. This work sheds light on phase-transition engineering and offers a convenient route to construct heterointerfaces for large-scale HER production. 相似文献
Microwave heating was employed to prepare highly dispersed Pt/C catalyst. Uniform platinum nanoparticles with average diameter of about 3.0-5.0 nm dispersed on carbon materials (XC-72) were synthesized using a domestic microwave oven. Synthesized Pt/C materials were characterized by X-ray diffraction and transmission electron microscopy. The particle size and size distribution of Pt nanoparticles greatly depend on microwave irradiation duration, where the heating temperature rises rapidly as the process proceeds. Cyclic voltammetry demonstrates that Pt/C catalysts derived from microwave irradiation for 90 s exhibits higher catalytic activity than a commercial Pt/C catalyst (E-Tek) at room temperature. The improvement in electrocatalytic activity of synthesized Pt/C materials is attributed to uniformity of particle size, well dispersion and high surface area, which is obtained around 175 °C and irradiation for 90 s. 相似文献
Noble metal‐based catalysts are currently widely used for the dehydrogenation of hydrocarbons or the production of H2 from hydrocarbons for various applications. However, these catalysts are expensive and hard to scale up. In this work, a facile template‐assisted synthesis of hollow carbon microspheres possessing ultrasmall molybdenum carbide (Mo2C) nanoparticles (NPs) that can efficiently catalyze the dehydrogenation of hydrocarbons is reported. The hollow structures and catalytic activity of the materials can be tuned, or optimized, by controlling the relative amount of Mo species or template used in their precursors. The bowl‐like hemispherical carbons with ≈20 nm thin shells and <5 nm in diameter Mo2C NPs show superior catalytic activity for dehydrogenation of cyclohexane, with a turnover frequency value of 1 × 10−4 s−1 at 305 °C. The catalytic activity of these microspheres for the reaction is 15 times higher than that of the corresponding incomplete hollow spherical carbon microparticles possessing similar sized Mo2C NPs and also better than that of activated carbon‐supported Pt (Pt/AC). Interestingly also, adding a mere 0.1% Pt into the materials leads to several‐fold increase in their catalytic activity and much higher activity than that of Pt/AC. 相似文献
Platinum is one of the best-performing catalysts for the hydrogen evolution reaction (HER). However, high cost and scarcity severely hinder the large-scale application of Pt electrocatalysts. Constructing highly dispersed ultrasmall Platinum entities is thereby a very effective strategy to increase Pt utilization and mass activities, and reduce costs. Herein, highly dispersed Pt entities composed of a mixture of Pt single atoms, clusters, and nanoparticles are synthesized on mesoporous N-doped carbon nanospheres. The presence of Pt single atoms, clusters, and nanoparticles is demonstrated by combining among others aberration-corrected annular dark-field scanning transmission electron microscopy, X-ray absorption spectroscopy, and electrochemical CO stripping. The best catalyst exhibits excellent geometric and Pt HER mass activity, respectively ≈4 and 26 times higher than that of a commercial Pt/C reference and a Pt catalyst supported on nonporous N-doped carbon nanofibers with similar Pt loadings. Noteworthily, after optimization of the geometrical Pt electrode loading, the best catalyst exhibits ultrahigh Pt and catalyst mass activities (56 ± 3 A mg−1Pt and 11.7 ± 0.6 A mg−1Cat at −50 mV vs. reversible hydrogen electrode), which are respectively ≈1.5 and 58 times higher than the highest Pt and catalyst mass activities for Pt single-atom and cluster-based catalysts reported so far. 相似文献
Electrocatalytic hydrogen evolution reaction (HER) in alkaline media is important for hydrogen economy but suffers from sluggish reaction kinetics due to a large water dissociation energy barrier. Herein, Pt5P2 nanocrystals anchoring on amorphous nickel phosphate nanorods as a high-performance interfacial electrocatalyst system (Pt5P2 NCs/a-NiPi) for the alkaline HER are demonstrated. At the unique polycrystalline/amorphous interface with abundant defects, strong electronic interaction, and optimized intermediate adsorption strength, water dissociation is accelerated over abundant oxophilic Ni sites of amorphous NiPi, while hydride coupling is promoted on the adjacent electron-rich Pt sites of Pt5P2. Meanwhile, the ultra-small-sized Pt5P2 nanocrystals and amorphous NiPi nanorods maximize the density of interfacial active sites for the Volmer–Tafel reaction. Pt5P2 NCs/a-NiPi exhibits small overpotentials of merely 9 and 41 mV at −10 and −100 mA cm−2 in 1 M KOH, respectively. Notably, Pt5P2 NCs/a-NiPi exhibits an unprecedentedly high mass activity (MA) of 14.9 mA µgPt−1 at an overpotential of 70 mV, which is 80 times higher than that of Pt/C and represents the highest MA of reported Pt-based electrocatalysts for the alkaline HER. This work demonstrates a phosphorization and interfacing strategy for promoting Pt utilization and in-depth mechanistic insights for the alkaline HER. 相似文献
As cost-effective catalysts, platinum (Pt) single-atom catalysts (SACs) have attracted substantial attention. However, most studies indicate that Pt SACs in acidic hydrogen evolution reaction (HER) follow the slow Volmer-Heyrovsky (VH) mechanism instead of the fast kinetic Volmer-Tafel (VT) pathway. Here, this work propose that the VH mechanism in Pt SACs can be switched to the faster VT pathway for efficient HER by correlating Pt single atoms (SAs) with Pt clusters (Cs). Our calculations reveal that the correlation between Pt SAs and Cs significantly impacts the electronic structure of exposed Pt atoms, lowering the adsorption barrier for atomic hydrogen and enabling a faster VT mechanism. To validate these findings, this work purposely synthesize three catalysts: l-Pt@MoS2, m-Pt@MoS2 and h-Pt@MoS2 with low, moderate, and high Pt-loading, having different distributions of Pt SAs and Cs. The m-Pt@MoS2 catalyst with properly correlating Pt SAs and Cs exhibits outstanding performance with an overpotential of 47 mV and Tafel slope of 32 mV dec−1. Further analysis of the Tafel values confirms that the m-Pt@MoS2 sample indeed follows the VT reaction mechanism, aligning with the theoretical findings. This study offers a deep understanding of the synergistic mechanism, paving a way for designing novel-advanced catalysts. 相似文献
Electrochemical water splitting is considered as a promising approach to produce clean and sustainable hydrogen fuel. As a new class of nanomaterials with high ratio of surface atoms and tunable composition and electronic structure, metal clusters are promising candidates as catalysts. Here, a new strategy is demonstrated to synthesize active and stable Pt-based electrocatalysts for hydrogen evolution by confining Pt clusters in hollow mesoporous carbon spheres (Pt5/HMCS). Such a structure would effectively stabilize the Pt clusters during the ligand removal process, leading to remarkable electrocatalytic performance for hydrogen production in both acidic and alkaline solutions. Particularly, the optimal Pt5/HMCS electrocatalyst exhibits 12 times the mass activity of Pt in commercial Pt/C catalyst with similar Pt loading. This study exemplifies a simple yet effective approach to improve the cost effectiveness of precious-metal-based catalysts with stabilized metal clusters. 相似文献
Phase‐transition‐induced electronic structure and geometry‐modulation‐increased edge sites are of great importance for boosting the electrocatalytic activity of MoSe2 toward hydrogen evolution reaction (HER). However, little efforts have been made to improve the intrinsic activity on per‐catalytic site of MoSe2 for HER. In this work, the electrocatalytic HER activities of MoSe2 are extremely enhanced by simple incorporation of boron which can reasonably engineer the electron transfer from Mo atoms to the active sites including B and Se atoms. Compared with the pristine 1T MoSe2, the as‐opimized B‐1T MoSe2 nanosheets show a reduced overpotential of 180 mV at current density of 10 mA cm−2, a lowered Tafel slope of 50.6 mV dec−1, and increased turnover frequency under a constant overpotential. While the electrochemical surface area of the catalyst after B‐incorporation is decreased, the improved inherent activity on per‐catalytic site and facilitated HER kinetics are demonstrated. The results pave the way to reasonably engineer the electron transfer to the active sites in the catalysts by B‐doping to boost the intrinsic activity on per‐catalytic site for electrocatalytic HER. 相似文献
Recently, the use of Pt in the form of single atoms (SA) has attracted considerable attention to promote the cathodic hydrogen production reaction from water in electrochemical or photocatalytic settings. First, produce suitable electrodes by Pt SA deposition on Direct current (DC)-sputter deposited titania (TiO2) layers on graphene—these electrodes allow to characterization of the electrochemical properties of Pt single atoms and their investigation in high-resolution HAADF-STEM. For Pt SAs loaded on TiO2, electrochemical H2 evolution shows only a very small overpotential. Concurrent with the onset of H2 evolution, agglomeration of the Pt SAs to clusters or nanoparticles (NPs) occurs. Potential cycling can be used to control SA agglomeration to variable-size NPs. The electrochemical activity of the electrode is directly related to the SA surface density (up to reaching the activity level of a plain Pt sheet). In contrast, for photocatalytic H2 generation already a minimum SA density is sufficient to reach control by photogenerated charge carriers. In electrochemical and photocatalytic approaches a typical TOF of ≈100–150 H2 molecules per second per site can be reached. Overall, the work illustrates a straightforward approach for reliable electrochemical and photoelectrochemical investigations of SAs and discusses the extraction of critical electrochemical factors of Pt SAs on titania electrodes. 相似文献
Cost-effective electrocatalysts for the hydrogen evolution reaction (HER) play a key role in the field of renewable energy. Although tremendous efforts have been devoted to the search of alternative materials, Pt/C is still the most efficient electrocatalyst for the HER. Nevertheless, decreasing the loading of Pt in the designed eletrocatalysts is of significance. However, with low Pt loading, it is challenging to maintain excellent catalytic performance. Herein, a new catalyst (Pt/NPC) was prepared by dispersing Pt nanoparticles (PtNPs) with an average diameter of 1.8 nm over a three-dimensional (3D) carbon network co-doped with N and P. Because of the high electronegativity of the N and P dopants, PtNPs were uniformly dispersed on the carbon network via high electronic affinity between Pt and carbon, affording a Pt/NPC catalyst; Pt/NPC exhibited superior HER activity, attributed to the down-shift of the Pt d-band caused by the donation of charge from N and P to Pt. The results show that Pt/NPC with an ultralow Pt loading of 1.82 wt.% exhibits excellent HER performance, which corresponds to a HER mass activity 20.6-fold greater than that observed for commercial 20% Pt/C at an overpotential of 20 mV vs. RHE.
High gravimetric energy density, earth-abundance, and environmental friendliness of hydrogen sources have inspired the utilization of hydrogen fuel as a clean alternative to fossil fuels. Hydrogen evolution reaction (HER), a half reaction of water splitting, is crucial to the low-cost production of pure H2 fuels but necessitates the use of electrocatalysts to expedite reaction kinetics. Owing to the availability of low-cost oxygen evolution reaction (OER) catalysts for the counter electrode in alkaline media and the lack of low-cost OER catalysts in acidic media, researchers have focused on developing HER catalysts in alkaline media with high activity and stability. Nickel is well-known as an HER catalyst and continuous efforts have been undertaken to improve Ni-based catalysts as alkaline electrolyzers. In this review, we summarize earlier studies of HER activity and mechanism on Ni surfaces, along with recent progress in the optimization of the Ni-based catalysts using various modern techniques. Recently developed Ni-based HER catalysts are categorized according to their chemical nature, and the advantages as well as limitations of each category are discussed. Among all Ni-based catalysts, Ni-based alloys and Ni-based hetero-structure exhibit the most promising electrocatalytic activity and stability owing to the fine-tuning of their surface adsorption properties via a synergistic nearby element or domain. Finally, selected applications of the developed Ni-based HER catalysts are highlighted, such as water splitting, the chloralkali process, and microbial electrolysis cell.
Transition metal carbide (TMC) nanomaterials are promising alternatives to Pt,and are widely used as heterogeneous electrocatalysts for the electrochemical hydrogen evolution reaction (HER).In this work,a bromide-induced wet-chemistry strategy to synthesize Co2C nanopartides (NPs) was developed.Such NPs exhibited high electrocatalytic activity (η =181 mV for j =-10 mA.cm-2) and long-term stability (no obvious performance decrease after 4,000 cycles) for the HER.This study will pave the way for the design and fabrication of TMC NPs via a wetchemistry method,and will have significant impacts on broader areas such as nanocatalysis and energy conversion. 相似文献
Vapor-based deposition techniques are emerging approaches for the design of carbon-supported metal powder electrocatalysts with tailored catalyst entities, sizes, and dispersions. Herein, a pulsed CVD (Pt-pCVD) approach is employed to deposit different Pt entities on mesoporous N-doped carbon (MPNC) nanospheres to design high-performance hydrogen evolution reaction (HER) electrocatalysts. The influence of consecutive precursor pulse number (50-250) and deposition temperature (225–300 °C) are investigated. The Pt-pCVD process results in highly dispersed ultrasmall Pt clusters (≈1 nm in size) and Pt single atoms, while under certain conditions few larger Pt nanoparticles are formed. The best MPNC-Pt-pCVD electrocatalyst prepared in this work (250 pulses, 250 °C) reveals a Pt HER mass activity of 22.2 ± 1.2 A mg−1Pt at -50 mV versus the reversible hydrogen electrode (RHE), thereby outperforming a commercially available Pt/C electrocatalyst by 40% as a result of the increased Pt utilization. Remarkably, after optimization of the Pt electrode loading, an ultrahigh Pt mass activity of 56 ± 2 A mg−1Pt at -50 mV versus RHE is found, which is among the highest Pt mass activities of Pt single atom and cluster-based electrocatalysts reported so far. 相似文献
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