Electrocatalytic Activity For Hydrogen Evolution Research Articles

In Situ “Chainmail Catalyst” Assembly in Low‐Tortuosity, Hierarchical Carbon Frameworks for Efficient and Stable Hydrogen Generation

AbstractThe chainmail catalysts (transition metals or metal alloys encapsulated in carbon) are regarded as stable and efficient electrocatalysts for hydrogen generation. However, the fabrication of chainmail catalysts usually involves complex chemical vapor deposition (CVD) or prolonged calcination in a furnace, and the slurry‐based electrode assembly of the chainmail catalysts often suffers from inferior mass transfer and an underutilized active surface. In this work, a freestanding wood‐based open carbon framework is designed embedded with nitrogen (N) doped, few‐graphene‐layer‐encapsulated nickel iron (NiFe) alloy nanoparticles (N‐C‐NiFe). 3D wood‐derived carbon framework with numerous open and low‐tortuosity lumens, which are decorated with carbon nanotubes (CNTs) “villi”, can facilitate electrolyte permeation and hydrogen gas removal. The chainmail catalysts of the N‐C‐NiFe are uniformly in situ assembled on the CNT “villi” using a rapid heat shock treatment. The high heating and quenching rates of the heat shock method lead to formation of the well‐dispersed ultrafine nanoparticles. The self‐supported wood‐based carbon framework decorated with the chainmail catalyst displays high electrocatalytic activity and superior cycling durability for hydrogen evolution. The unique heat shock method offers a promising strategy to rapidly synthesize well‐dispersed binary and polynary metallic nanoparticles in porous matrices for high‐efficiency electrochemical energy storage and conversion.

Interface Designing over WS2/W2C for Enhanced Hydrogen Evolution Catalysis

Interface engineering is a promising strategy for boosting the catalytic performances via the optimized coordination. Herein, we developed a top-down strategy to in situ obtain the nanocomposite of N, S-decorated porous carbon matrix encapsulated WS2/W2C (WS2/W2C@NSPC). The as-synthesized hybrid is characterized by excellent interface coupling in atomic level, good electrical conductivity, and high active surface area. Electrochemical measurements show that the optimized catalyst exhibits remarkable electrocatalytic activity for hydrogen evolution in both acidic and alkaline media. These results should be attributed to the abundant active sites existing in the different phase boundaries, resulting from a synergistic effect of the activated WS2/W2C heterostructure and the highly conductive carbon matrix. This strategy opens new avenues toward understanding the relationship between chemical structure and catalytic performance in molecular level and thus providing a rational way to fabricate highly efficient...

A novel composite of network-like tungsten phosphide nanostructures grown on carbon fibers with enhanced electrocatalytic hydrogen evolution efficiency

Enhancing the electrocatalytic activity of transition metal phosphides (TMPs) for hydrogen evolution has become an attractive way for noble-metal-free electrocatalysts. In this work, a novel composite of network-like tungsten phosphide nanostructures on carbon fibers (CFs@WP) was prepared by a two-step high-temperature calcination strategy. Owing to the high electrochemical active surface area originating from the WP nanostructures of network-like morphology and the enhanced conductivity caused by the introduction of carbon fibers, the obtained CFs@WP composite, as an integrated hydrogen evolution cathode, exhibits much higher electrocatalytic activity for hydrogen evolution than pure WP nano-/micro-particles after toasting their corresponding suspension onto bare CFs. This catalyst could, in 0.5 mol·L−1 H2SO4, deliver a current density of 10 and 100 mA·cm−2 respectively at the over-potential of merely 137 mV and 215 mV, and present a small Tafel slope of 69 mV·dec−1 as well as excellent stability at various current densities, although it may exhibit relatively inferior catalytic activity in hydrogen evolution in neutral and alkaline conditions. The present strategy may also offer a straight-forward model to enhance the hydrogen evolution activity of other TMPs catalysts.

Targeted bottom-up synthesis of 1T-phase MoS2 arrays with high electrocatalytic hydrogen evolution activity by simultaneous structure and morphology engineering

The incorporation of small guest molecules or ions by bottom-up hydrothermal synthesis has recently emerged as a promising new way to engineer 1T-phase MoS2 with high hydrogen evolution reaction (HER) activity. However, the mechanism of the associated structural evolution remains elusive and controversial, leading to a lack of effective routes to prepare 1T-phase MoS2 with controlled structure and morphology, along with high purity and stability. Herein, urea is chosen as precursor of small molecules or ions to simultaneously engineer the phase (~16.4%, ~69.4%, and ~90.2% of 1T phase) and size (~98.8, ~151.6, and ~251.8 nm for the 90.2% 1T phase) of MoS2 nanosheets, which represent an ideal model system for investigating the structural evolution in these materials, as well as developing a new type of 1T-phase MoS2 arrays. Using reaction intermediate monitoring and theoretical calculations, we show that the oriented growth of 1T-phase MoS2 is controlled by ammonia-assisted assembly, recrystallization, and stabilization processes. A superior HER performance in acidic media is obtained, with an overpotential of only 76 mV required to achieve a stable current density of 10 mA·cm–2 for 15 h. This excellent performance is attributed to the unique array structure, involving well-dispersed, edge-terminated, and high-purity 1T-phase MoS2 nanosheets.

Controllable Edge Exposure of MoS2 for Efficient Hydrogen Evolution with High Current Density

MoS2-based electrocatalysts are promising cost-effective replacements for Pt-based catalysts for hydrogen evolution by water splitting, yet achieving high current density at low overpotential remains a challenge. Herein, a binder-free electrode of MoS2/CNF (carbon nanofiber) is prepared by electrospinning and subsequent thermal treatment. The growth of MoS2 nanoplates contained within or protruding out from the CNF can be controlled by adding urea or ammonium bicarbonate to the electrospinning precursors, due to the cross-linking effects of urea and the increased porosity caused by pyrolysis of ammonium bicarbonate allowing growth through pores in the CNF. By virtue of the abundant exposed edges in this microstructure and strong bonding between the catalyst and the conductive carbon network, the composite material exhibits ultrahigh electrocatalytic hydrogen evolution activity in acidic solutions, with current densities of 500 and 1000 mA/cm2 at overpotentials of 380 and 450 mV, respectively, exceeding th...

One-Step Preparation of Large Area Films of Oriented MoS₂ Nanoparticles on Multilayer Graphene and Its Electrocatalytic Activity for Hydrogen Evolution.

MoS2 is a promising material to replace Pt-based catalysts for the hydrogen evolution reaction (HER), due to its excellent stability and high activity. In this work, MoS2 nanoparticles supported on graphitic carbon (about 20 nm) with a preferential 002 facet orientation have been prepared by pyrolysis of alginic acid films on quartz containing adsorbed (NH4)2MoS4 at 900 °C under Ar atmosphere. Although some variation of the electrocatalytic activity has been observed from batch to batch, the MoS2 sample exhibited activity for HER (a potential onset between 0.2 and 0.3 V vs. SCE), depending on the concentrations of (NH4)2MoS4 precursor used in the preparation process. The loading and particle size of MoS2, which correlate with the amount of exposed active sites in the sample, are the main factors influencing the electrocatalytic activity.

Hydrothermal synthesis of ternary MoS2xSe2(1−x) nanosheets for electrocatalytic hydrogen evolution

MoS2xSe2(1−x) nanosheets exhibit promising electrocatalytic hydrogen evolution activity in acidic media.

Photoelectrochemical hydrogen generation employing a Cu2O-based photocathode with improved stability and activity by using NixPy as the cocatalyst.

With the tactical integration of band edge energetics concepts in semiconducting films to reduce charge recombination and photocorrosion, an improvement in the photocurrent can be achieved by introducing CuO and NixPy into Cu2O films. Photodegradation limitations of Cu2O are overcome by the Cu2O-CuO-NixPy photocathode. NixPy, because of its excellent electrocatalytic hydrogen evolution activity, helps in obtaining better stability and activity. The individual effects of CuO and NixPy have been investigated and it is found that the activity enhancement stems mainly from the contribution of NixPy, whereas CuO helps with the unidirectional flow of photogenerated charges to prevent the photocorrosion of Cu2O. Relative to bare and modified Cu2O, Cu2O-CuO-NixPy shows a considerable reduction in the overpotential and a remarkable improvement in the photocurrent at 0 V (vs. RHE). This is the first report on the use of NixPy as the co-catalyst in a Cu2O based photocathode system to improve its photostability as well as its activity.

Enhanced electrocatalytic hydrogen evolution activity of nickel foam by low-temperature-oxidation

Abstract

Electrocatalytic Hydrogen Evolution and Hydrogen Oxidation with a Ni(PS)2 Complex

Tetra‐coordinate NiII and ZnII complexes employing the PS chelates 2‐(diphenylphosphanyl)benzenethiol (HL1) and 2‐(diisopropylphosphanyl)benzenethiol (HL2) have been synthesized and characterized by spectroscopic, structural, and electrochemical methods. All complexes were screened for electrocatalytic activity for hydrogen evolution with acetic acid and hydrochloric acid and hydrogen oxidation in the presence of triethylamine. The nickel complex Ni(L1)2 (1) was found to reduce protons from external acids to generate hydrogen with a turnover frequency of 140 s–1 at an overpotential of 1.1 V and cleave dihydrogen using redox active base triethylamine (Et3N) with a turnover frequency of 23 s–1 at an overpotential of 0.33 V. Ni(L2)2 (3) was also found to be an active catalyst for dihydrogen oxidation, but inefficient for proton reduction due to inaccessible Ni (II/I) reduction in the potential window. Zn(L1)2 (2) and Zn(L2)2 (4) complexes were found to be inadequate for their electrocatalytic behaviour towards both the reactions.

Template-synthesis and electrochemical properties of urchin-like NiCoP electrocatalyst for hydrogen evolution reaction

Herein, we report a template-engaged strategy to fabricate urchin-like ternary metal phosphide (Ni0.5Co0.5P-300) as catalyst for hydrogen evolution reaction. The morphology and microstructure of Ni0.5Co0.5P-300 and its precursors were examined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and micropore and chemisorption analyzer. Electrochemical properties were characterized by typical electrochemical methods, such as linear sweep voltammetry, cyclic voltammetry, chronoamperometry, chronopotentiometry and electrochemical impedance spectroscopy on a standard three-electrode system. Results show that the developed porous hierarchical 3D Ni0.5Co0.5P-300 catalyst has excellent electrocatalytic activity for hydrogen evolution in alkaline aqueous solution with onset overpotential of 26mV and Tafel slope of 58mV at the loading mass of 0.28mgcm−2. It only needs 87mV to reach the current density of 10mAcm−2 and can hold the nearly unchanged current density for 25h amperometric test. Meanwhile, the Ni0.5Co0.5P-300 catalyst also exhibits good electrocatalytic properties for hydrogen evolution in 1M PBS solution (pH=7). These indicate that the Ni0.5Co0.5P-300 catalyst with urchin-like structure, bimetallic merit, and low cost may be a good candidate as electrocatalyst in practical application of hydrogen evolution.

One-pot synthesis of hollow AgPt alloyed nanocrystals with enhanced electrocatalytic activity for hydrogen evolution and oxygen reduction reactions

Herein, a simple one-pot aqueous method was developed for the fabrication of uniform hollow bimetallic AgPt alloyed nanocrystals (H-AgPt NCs) by using 5-aminoorotic acid (5-amino-2,6-dioxo-1,2,3,6-tetrahydropyrimidine-4-carboxylic acid) as a growth-directing agent, without any seed, organic solvent or template involved. The prepared H-AgPt NCs displayed enhanced electrocatalytic activity for hydrogen evolution reaction (HER) with a more positive onset overpotential (ηonset) of −28mV and a smaller Tafel slope of 40mVdec−1 relative to commercial Pt black (−34mV, 50mVdec−1) and Pt/C (20wt.%, −33mV, 33mVdec−1) in 0.5M H2SO4. Meanwhile, the obtained catalyst exhibited improved catalytic features toward oxygen reduction reaction (ORR) with a positive ηonset (0.916V) and enhanced kinetic current density (243.23mAmg−1Pt) in 0.1M HClO4 at 0.850V compared with Pt black (0.876V, 25.85mAmg−1Pt).

Rapid fabrication of support-free trimetallic Pt53Ru39Ni8 nanosponges with enhanced electrocatalytic activity for hydrogen evolution and hydrazine oxidation reactions

Herein, a rapid and straightforward coreduction aqueous approach was developed for preparation of support-free trimetallic Pt53Ru39Ni8 nanosponges with clean surface. Plenty of hydrogen bubbles were in situ formed via the oxidation and hydrolysis of the reductant (sodium borohydride), which served as the dynamic template in the fabrication of the porous sponge-like structures. The shape, size, crystal structure, and composition of the products were characterized by a set of characterization techniques. The obtained Pt53Ru39Ni8 nanosponges displayed dramatically highly electrocatalytic performances for hydrogen evolution reaction (HER) and hydrazine oxidation reaction (HOR) outperformed home-made PtNi nanoparticles (PtNi NPs), RuNi NPs and commercial PtRu black (50wt.%). The present route provides new insights for facile synthesis of other bi-, tri- and even multi-metallic nanocatalysts for potential applications in catalysis, energy conversion and storage.

Enhancing Electrocatalytic Activity for Hydrogen Evolution by Strongly Coupled Molybdenum Nitride@Nitrogen-Doped Carbon Porous Nano-Octahedrons

Developing highly efficient and affordable noble-metal-free catalysts toward the hydrogen evolution reaction (HER) is an important step toward the economical production of hydrogen. As a nonprecious-metal catalyst for the HER, molybdenum nitride (MoN) has excellent corrosion resistance and high electrical conductivity, but its catalytic activity is still inadequate. Here we report our findings in dramatically enhancing the HER activity of MoN by creating porous MoN@nitrogen-doped carbon (MoN-NC) nano-octahedrons derived from metal–organic frameworks (MOFs). The composite catalyst displays remarkably high catalytic activity, demonstrating a low overpotential of 62 mV at a current density of 10 mA cm–2 (η10), a small Tafel slope of 54 mV dec–1, and a large exchange current density of 0.778 mA cm–2 while maintaining good stability. The enhancement in catalytic properties is attributed to the unique nanostructure of the MoN, the high porosity of the electrode, and the synergistic effect between the MoN and th...

Colloidal synthesis of MoSe2 nanonetworks and nanoflowers with efficient electrocatalytic hydrogen-evolution activity

MoSe2 represents an important layered transition metal dichalcogenides (LTMDs) that have high electrocatalytic activity in hydrogen evolution reaction (HER). A key issue to achieve excellent electrochemical properties of MoSe2 is to synthesize nanostructures that are composed of few-layer MoSe2 with maximized exposure of active edge sites. In this study, we report the synthesis of MoSe2 nanostructures with network-like and flower-like morphologies via an organic solution approach that utilizes molybdenum hexacarbonyl as Mo precursor and Se powders as Se source. The prepared MoSe2 nanostructures consist of few-layer ultrathin nanosheets which can have different orientations. Depending on the volume ratio of oleylamine to oleic acid, the arrangement of ultrathin MoSe2 nanosheets is adjustable and can form porous network-like or discrete flower-like nanostructure which has large specific surface area and a wealth of exposed edge sites. Excellent HER activities with low overpotentials, small Tafel slopes and long-term durability are observed on the as-synthesized MoSe2 nanostructures. The acetic acid-washing step that may effectively remove the organic molecules capped on MoSe2 surfaces is also found to be efficient in improving the HER activity of the synthesized MoSe2 nanostructures.

Graphitized carbon-coated vanadium carbide nanoboscages modified by nickel with enhanced electrocatalytic activity for hydrogen evolution in both acid and alkaline solutions

Three-dimensional Ni-modified VC nanoboscages with graphitic carbon coating structures were controllably synthesized as a highly active HER catalyst by inventively employing metallic Ni as a crystalline inducer.

Improving the intrinsic electrocatalytic hydrogen evolution activity of few-layer NiPS3 by cobalt doping.

Here we demonstrate the improvement of the intrinsic electrocatalytic hydrogen evolution activity of NiPS3 by proper cobalt doping. The optimized Ni0.95Co0.05PS3 nanosheets display a geometric catalytic current density of -10 mA cm-2 at an overpotential of 71 mV vs. RHE and a Tafel slope of 77 mV dec-1 in 1.0 M KOH.

High Electrocatalytic Hydrogen Evolution Activity of an Anomalous Ruthenium Catalyst.

Hydrogen evolution reaction (HER) is a critical process due to its fundamental role in electrocatalysis. Practically, the development of high-performance electrocatalysts for HER in alkaline media is of great importance for the conversion of renewable energy to hydrogen fuel via photoelectrochemical water splitting. However, both mechanistic exploration and materials development for HER under alkaline conditions are very limited. Precious Pt metal, which still serves as the state-of-the-art catalyst for HER, is unable to guarantee a sustainable hydrogen supply. Here we report an anomalously structured Ru catalyst that shows 2.5 times higher hydrogen generation rate than Pt and is among the most active HER electrocatalysts yet reported in alkaline solutions. The identification of new face-centered cubic crystallographic structure of Ru nanoparticles was investigated by high-resolution transmission electron microscopy imaging, and its formation mechanism was revealed by spectroscopic characterization and theoretical analysis. For the first time, it is found that the Ru nanocatalyst showed a pronounced effect of the crystal structure on the electrocatalytic activity tested under different conditions. The combination of electrochemical reaction rate measurements and density functional theory computation shows that the high activity of anomalous Ru catalyst in alkaline solution originates from its suitable adsorption energies to some key reaction intermediates and reaction kinetics in the HER process.

Ternary Transitional Metal Chalcogenide Nanosheet with Significantly Enhanced Electrocatalytic Hydrogen-Evolution Activity

Electrochemical production of hydrogen from water holding tremendous promise for clean energy has been directed to the search for non-noble metal based and earth-abundant catalysts. Here we report dramatically enhanced HER catalysis of ternary I-Cu2WS4 nanosheets from chemically exfoliated via lithium intercalation. Structural characterization and electrochemical study confirmed that the enhanced electrocatalytic activity of I-Cu2WS4 nanosheets is associated with the larger surface area to provide an easy path for the hopping of electrons. This study opens a new way for the development of ternary highly active non-noble electrocatalysts for hydrogen production from water splitting.

Formation of Ni-Co-MoS2 Nanoboxes with Enhanced Electrocatalytic Activity for Hydrogen Evolution.

Nickel and cobalt incorporated MoS2 nanoboxes are synthesized via the reaction between Ni-Co Prussian blue analogue nanocubes and ammonium thiomolybdate. Due to the structural and compositional advantages, these well-defined nanoboxes manifest enhanced electrochemical activity as an electrocatalyst for hydrogen evolution reaction.