High Electrocatalytic Activity For Hydrogen Evolution Reaction Research Articles

Co-deposition of Co-Fe alloy catalysts for hydrogen evolution reaction based on ethylene glycol system

The co-deposition behavior of Co+2 and Fe+2 in ethylene glycol (EG) are investigated using cyclic voltammetry (CV) techniques. These results imply that Co+2 species can accelerate the Co-Fe co-deposition, while Fe+2 can inhibit the reduction of Co+2. Moreover, the two effects can be improved as Co+2 or Fe+2 concentration increases. Microstructural and compositional characteristics of the samples show that Co-Fe deposits with various Fe content can be obtained from anhydrous FeCl2 and CoCl2 in EG. Scanning electron microscopy imaging of the surfaces of these Co-Fe alloy coatings shows that they present a dense structure with spherical “nodules”, the size of which is related to the Fe content. The electrocatalytic activity for hydrogen evolution reaction (HER) on the Co-Fe coatings is also investigated. These results indicate that its electrocatalytic activity can be improved as Fe contents increase from 2.2 to 9.8 wt.% and the Co-Fe alloy with 9.8 wt.% Fe exhibits the high electrocatalytic activity for HER with an overpotential of 124 mV at 10 mA cm−2 in 1 M KOH.

Comparing electrocatalytic hydrogen and oxygen evolution activities of first-row transition metal complexes with similar coordination environments

Developing cheap and efficient electrocatalysts for water splitting is required for energy conversion techniques. Many first-row transition metal complexes have been shown to be active for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Metal ions play crucial roles in these catalytic processes, but the activity dependence on the nature of metal ions has been rarely studied due to the difficulty to compare metal complexes with different coordination environments. We herein reported the synthesis of a series of metal complexes of azido-substituted porphyrin (1), in which metal ions have very similar coordination environments. By grafting 1-M (M = Mn, Fe, Co, Ni, and Cu) onto alkyne-functionalized carbon nanotubes (CNTs) through the same covalent connection, the resulted hybrids 1-M@CNT were all active and robust for both electrocatalytic HER and OER in alkaline aqueous solutions. Among these hybrids, 1-Fe@CNT displayed the highest electrocatalytic activity for HER, while 1-Co@CNT was the most active one for OER. Moreover, a two-electrode water electrolysis cell assembled with 1-Fe@CNT as the cathode and 1-Co@CNT as the anode required smaller applied bias potential by 210 mV to get 10 mA/cm2 current density as compared to that assembled with Pt/C and Ir/C with the same amount of metal loading. This work is significant to correlate HER and OER activity with the nature of first-row transition metal ions and to highlight promising potential applications of molecular electrocatalysis in water splitting.

Multi-Element Containing Precious Group Metal-Free Electrocatalysts for Efficient Hydrogen Evolution Reaction in PEM Water Electrolysis

Electricity driven proton exchange membrane-based water electrolysis (PEMWE) has demonstrated considerable credibility in recent years, establishing high competency enabling PEMWE technology for rapid generation of clean hydrogen fuel 1-7. In order to attain the high efficiency needed and successful commercialization of PEMWE, there is a critical need to identify highly active, robust, and earth-abundant electrocatalysts for accelerating the hydrogen evolution reaction (HER) with minimum energy input 8. In the pursuit of achieving this goal, in the present work, employing the density functional theory (DFT) based calculations for rationalizing the thermodynamics and reaction kinetics of HER, we have investigated the platinum group metal (PGM)-free, earth-abundant, transition metal non-oxide (TMN) based electrocatalysts for acid mediated HER in PEMWE. Based on the theoretical calculations, the as-synthesized TMN electrocatalyst compositions reveal optimized hydrogen adsorption free energies (ΔGH *) and beneficial electronic structures modification, offering superior charge transfer kinetics, lower reaction barrier, low water contact angle (7o) suggesting high wettability (Fig. 1), and high electrocatalytic activity for HER. Furthermore, the highly active electrocatalyst compositions display excellent long term electrochemical HER stability in acidic media, with no significant obvious degradation in current density. The as-synthesized electrocatalysts thus, has propensity for exhibiting robust HER performance with excellent structural and mechanical integrity. The experimental results are in excellent agreement with the DFT calculations which further accentuate the incorporation of suitable PGM-free dopants into the TMN compositions resulting in optimized electronic structures lowering the HER reaction barriers. The system therefore offers improved electrocatalytic performance for HER which is comparable to state-of-the-art Pt/C electrocatalysts. Accordingly, the as-synthesized PGM-free electrocatalysts can be considered as reliable HER candidates, vital for the development of acid mediated PEM based water splitting employing PGM-free electrocatalysts. Results of this study will be presented and discussed. Acknowledgements: Financial support of NSF-CBET grant# 1511390, Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) is acknowledged.

Controllable Synthesis of MoS2/Carbon Nanotube Hybrids with Enlarged Interlayer Spacings for Efficient Electrocatalytic Hydrogen Evolution

AbstractHydrogen, as a clean, affordable and reliable energy, is one of the important roles in clean energy conversion. In order to meet the demand of current energy, the hydrogen evolution reaction (HER) has attracted considerable attention as an effective process to produce hydrogen from water. Herein, we report a simple solvothermal synthesis of molybdenum disulfide (MoS2)/carbon nanotube (CNT) hybrids with enlarged interlayer distances ranging from 8.9 to 9.7 Å through controlling the CNTs loadings. The synergistic effects between CNTs and the layered MoS2 result in the high electrocatalytic activity for HER. MoS2/CNT‐2 catalyst with the enlarged lattice spacing of 9.7 Å shows the enhanced overpotential with 210 mV to reach the current density of 10 mA cm−2, 56 mV dec−1 Tafel slope, and good stability over 1000 cycles. This work provides a facile way to the fabrication of efficient MoS2‐based catalysts via modulating the interlayer spacing of MoS2 nanosheets.

Pulse electrodeposition of nickel selenide nanostructure as a binder-free and high-efficient catalyst for both electrocatalytic hydrogen and oxygen evolution reactions in alkaline solution

Herein, we report a pulse potential electrodeposition method (PPE) as a fast and one-step route for the production of effective and binder-free Ni–Se catalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline solution. The results demonstrated that the fabricated electrocatalysts by PPE show more desirable electrocatalytic performance than constant potential electrodeposition method (CPE). The electrodeposited NiSe nanostructures with large electrochemically active surface area of 2965 on the nickel foam (NF) at the frequency of 0.01 Hz exhibited high electrocatalytic activity for HER and OER. It delivers the current density of 10 mA/cm2 at the overpotential of 65 mV for HER and 100 mA/cm2 at 306 mV for OER in 1 M KOH. In addition, the Tafel slope for HER and OER was 89 and 61 mV/dec respectively. Morphological stability of NiSe nanostructure catalyst leads to an increase the electrocatalytic stability during long-term electrolysis.

Activated Cu/Cu2O foam with Ni nanoparticles for electrocatalytic activity enhancement of hydrogen evolution reaction (HER) in acidic media

This paper presents the hydrogen evolution reaction of Cu/Cu2O foam by Ni nanoparticles, deposited by electrodeposition and electroless plating. The structure and morphology of Cu/Cu2O foam and deposited Ni nanoparticles were studied by FE-SEM and XRD. The foam with Ni nanoparticles had a high specific surface area measured by BET. The synthesized Cu/Cu2O foam/Ni electrode presented high electrocatalytic activity for HER, with low overpotential of −290mV vs. Ag/AgCl and Tafel slope of 50mVdecade−1. The stability study of the developed electrodes showed a high stability in short-term.

Effect of TiO2 on electrocatalytic behavior of Ni-Mo alloy coating for hydrogen energy

Ni-Mo-TiO2 composite coating has been developed through electrodeposition method by depositing titanium dioxide (TiO2) nanoparticles parallel to the process of Ni-Mo alloy coating. The experimental results explaining the increased electrocatalytic activity of Ni-Mo alloy coating on incorporation of TiO2 nanoparticles into its alloy matrix is reported here. The effect of addition of TiO2 on composition, morphology and phase structure of TiO2 – composite coating is studied with special emphasis on its electrocatalytic activity for hydrogen evolution reaction (HER) in 1.0 M KOH solution. The electrocatalytic activity of alloy coatings were validated using cyclic voltammetry (CV) and chronopotentiometry (CP) techniques. Under optimal condition, TiO2 – composite alloy coating represented as (Ni-Mo-TiO2)2.0 A dm−2 is found to exhibit the highest electrocatalytic activity for HER compared to its binary alloy counterpart. The increased electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm−2 composite coating was attributed to the increased Mo content, porosity and roughness of coating, affected due to addition of TiO2 nanoparticles, supported by SEM, EDX, XRD and AFM study. The increased electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm−2 coating was found due to decreased Rct and increased Cdl values, demonstrated by EIS study. Better electrocatalytic activity of (Ni-Mo-TiO2)2.0 A dm−2 coating, compared to (Ni-Mo)2.0 A dm−2 coating has been explained through mechanism. Experimental study revealed that (Ni-Mo-TiO2)2.0 A dm−2 composite coating follows Volmer-Heyrovsky mechanism, compared to Tafel mechanism in case of (Ni-Mo-TiO2)2.0 A dm−2 coating, assessed on the basis of Tafel slopes.

Design of Electroactive Carbon Fibers Decorated with Metal and Metal‐Phosphide Nanoparticles for Hydrogen Evolution Technology

AbstractThe preparation of noble‐metal‐free electrode materials that enable the effective and economically viable hydrogen evolution reaction (HER) is proposed by using a needle‐less electrospinning method. Three transition metals (Ni, Co, Cu) capable of creation metal phosphides were stably incorporated into the carbon fibrous matrix. The electrode materials were prepared from low‐cost chemical reagents such as polyacrylonitrile, metal chlorides, and phosphoric acid. The embedded metal phosphides fundamentally influence the composition, microstructure, and porosity as evidenced by X‐ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses. The possible mechanisms for the formation and localization of nanoparticles were suggested. Linear sweep voltammetry, impedance spectroscopy, time of flight (TOF) calculation, and Tafel slope measurements in an acidic environment revealed that the highest electrocatalytic activity for HER was achieved in the carbon fibers decorated either with the cobalt/cobalt phosphide or copper/copper phosphide nanoparticles under heat treatment in a hydrogen atmosphere.

Magnetically Induced Electrodeposition of Ni-Mo Alloy for Hydrogen Evolution Reaction

The electrocatalytic activity of Ni-Mo alloy coatings for hydrogen evolution reaction (HER) was tried to increase by inducing the magnetic field (B), perpendicular to the process of deposition. The electrocatalytic activity of Ni-Mo alloys were studied by cyclic voltammetry (CV) and chronopotentiometry (CP) measurements in 1.0 M KOH medium. Ni-Mo alloy coatings developed at c.d. = 1.0 A dm−2 and B = 0.4 T was found to exhibit highest electrocatalytic activity for HER (with highest cathodic peak c.d. of −0.274 A cm−2 and least onset potential of −1.24 V and highest volume of H2 liberated, 14.0 mL), demonstrated by CV and CP experiments. The stability factor of Ni-Mo alloy coatings were evaluated through corrosion study. The experimental results showed that Ni-Mo alloy, electrodeposited in the presence of B, is more corrosion resistant than its conventional alloy, when tested in the same alkaline medium. The increase in the electrocatalytic activity of Ni-Mo alloy coatings, developed under induced B, is attributed to the structural and morphological changes, caused by an increase of Ni content in the alloy, evident from X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses.

Facile synthesis of molybdenum disulfide/nitrogen-doped graphene composites for enhanced electrocatalytic hydrogen evolution and electrochemical lithium storage

A facile one-pot hydrothermal route with the mediation of ionic liquid (IL, [BMIM]BF4) is presented to synthesize MoS2/nitrogen-doped graphene (MoS2/NG-IL) composites. It is found that as-prepared MoS2/NG-IL composites exhibit that the de-layered MoS2 sheets with more exposed edge sites and defects are well anchored on the N-doped graphene. Due to the synergism between de-layered MoS2 and N-doped graphene, MoS2/NG-IL composites exhibit better electrochemical performances for hydrogen evolution reaction (HER) and reversible lithium storage in comparison with MoS2. Especially, when 1.0 mL of IL is added in hydrothermal solution, the obtained MoS2/NG-IL10 displays very high electrocatalytic activity for HER with a low onset overpotential of 80 mV and a small Tafel slope of 48.0 mV/dec in 0.5 M H2SO4. As anode of lithium ion battery, MoS2/NG-IL10 delivers a reversible capacity as high as 1169 mAh g−1 at 100 mA g−1 and enhanced rate capability of 782 mAh g−1 at 1000 mA g−1. After 800 cycles, a reversible capacity of about 800 mAh g−1 at 500 mA g−1 can be retained, indicating its excellent cyclic stability.

Transition Metals (Co, Fe, Ni)-N-C Electrocatalysts for Hydrogen Evolution Reaction in Acidic and Alkaline Solutions

Hydrogen is one of the cleanest and most promising energy carriers as an alternative energy source.1, 2 The production of hydrogen from water via a hydrogen evolution reaction (HER) has been widely studied. Platinum is believed to have the highest electrocatalytic activity for HER in both acidic and alkaline solutions. But it is very expensive and rare. Thus, more advanced precious metal free electrocatalysts for HER are required to lower the cost of electrolyzers. 3, 4 In this study, carbon-based non-precious metal catalysts (Me-N-C) were synthesized by impregnating aniline and different metal salts into a carbon matrix and pyrolyzing at 900℃ in N2 atmosphere.5, 6 The structure of obtained composites were characterized by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. Their hydrogen evolution reaction (HER) activities were investigated in both 0.5 M H2SO4and 1 M KOH. For the first time, these non-precious metal electrocatalysts showed excellent activity for HER and good stability in both acidic and alkaline media. The Ni-C-N catalyst had the lowest onset potential while Co, Fe-C-N catalysts had smaller Tafel slopes than the former (Figure 1a). Various active sites could contribute to the HER activity in Me-N-C catalysts (Figure 1b). Density functional theory (DFT) calculations were employed to understand the activity enhancement mechanisms and identify the active center. This work paved a new route in the design of cheap, robust and high efficient catalysts to replace Pt. References Zhou, W.; Zhou, J.; Zhou, Y.; Lu, J.; Zhou, K.; Yang, L.; Tang, Z.; Li, L.; Chen, S. Chemistry of Materials 2015, 27, (6), 2026-2032.Fei, H.; Dong, J.; Arellano-Jiménez, M. J.; Ye, G.; Kim, N. D.; Samuel, E. L.; Peng, Z.; Zhu, Z.; Qin, F.; Bao, J. Nature communications 2015, 6.Deng, J.; Ren, P.; Deng, D.; Yu, L.; Yang, F.; Bao, X. Energy & Environmental Science 2014, 7, (6), 1919-1923.Zou, X.; Huang, X.; Goswami, A.; Silva, R.; Sathe, B. R.; Mikmeková, E.; Asefa, T. Angewandte Chemie 2014, 126, (17), 4461-4465.Merzougui, B.; Hachimi, A.; Akinpelu, A.; Bukola, S.; Shao, M. Electrochimica Acta 2013, 107, 126-132.Wu, G.; More, K. L.; Johnston, C. M.; Zelenay, P. Science 2011, 332, (6028), 443-447. Figure 1

MoO2 nanoparticles on reduced graphene oxide/polyimide-carbon nanotube film as efficient hydrogen evolution electrocatalyst

Hydrogen evolution reaction (HER) through low-cost and earth-abundant electrocatalysts at low overpotentials is a crucial project to clean energy. Molybdenum dioxide/reduced graphene oxide/polyimide-carbon nanotube (MoO2/RGO/PI-CNT) film was synthesized by a simple electrodeposition method as an efficient catalyst for HER. MoO2 nanoparticles with a small size of 10–20 nm uniformly disperse on the RGO surface. The large quantity and small size of MoO2 nanoparticles afford large surface area for HER, greatly enhancing the electrocatalytic performance of MoO2/RGO/PI-CNT film. The HER electrocatalytic property of MoO2/RGO/PI-CNT film in acidic solution is evaluated by linear sweep voltammetry (LSV). MoO2/RGO/PI-CNT film exhibit a high electrocatalytic activity for HER at a small onset overpotential (−110 mV vs RHE) with a high current density (10.0 mA cm−2) and a good stability. The low Tafel slope (68 mV dec−1) reveals the Volmer-Heyrovsky mechanism for HER. The comparison between MoO2/RGO/PI-CNT film and other catalysts indicate that the MoO2/RGO/PI-CNT film had a great performance for HER. This work presents a new thought for the synthesis of MoO2/RGO/PI-CNT film as an efficient HER electrocatalyst.

Preparation of Ni–CeO2 composite coatings with high catalytic activity for hydrogen evolution reaction

Ni–CeO2 composite coatings for hydrogen evolution reaction (HER) were electrodeposited under supergravity field from nickel sulfamate bath containing suspended nano-sized CeO2 particles. The prepared Ni–CeO2 composite coatings exhibit finer grain size and higher CeO2 content than that prepared under normal gravity condition. In addition, Tafel curves were determined to study the catalytic activity of composite coatings electrodeposited under different supergravity fields in 1M NaOH solution. The results indicated that Ni–CeO2 composite coating prepared under rotational speed 2350rpm presents the highest electrocatalytic activity for HER, and its exchange current density reaches 338.4μAcm−2, which is obviously better than the value ever reported in literature.

Hybrid Electrocatalysts of NiMo and Molybdenum Sulfide for Hydrogen Evolution Reaction

The best known catalysts for the hydrogen evolution reaction (HER) are platinum group precious metals, but the scarcity and high cost of these materials prohibit their wide-scale deployment.As a alternatives, nickel-based alloy (NiMo, NiW, NiFe etc.) catalysts show high electrocatalytic activity for HER, but they often degrade in acidic solutions.Recently, Molybdenum sulfides nanomaterials have drawn great attention due to their low cost, high chemical stability, and excellent photocatalytic and electrocatalytic properties in HERs. They are potentially useful if they can be tailored for the development of hydrogen energy devices. In order to enhance the efficiency of inorganic catalysts, many research efforts have been made toward the modification of material properties, the formation of composite catalysts, and the fabrication of the electrodes with nano-architecture.In this paper, we will show the hybrid electrocatalysts of NiMo nanoparticles and molybdenum sulfide thin films for HER, showing high activity and stability. The main purpose of this work is to draw the synergetic effect of NiMo's high activity and high electrical conductivity and molybdenum sulfide's high activity and high chemical stability.We synthesized NiMo nanoparticles and molybdenum sulfide thin films with various compositions. The electrodeposited molybdenum sulfide films had amorphous structure of MoSx and/or MoOSx. The electrochemical and spectroscopical analysis to understand the catalytic activity of hybrid catalysts will be discussed.

High electrocatalytic effect of Au–Pd alloy nanoparticles electrodeposited on microwave assisted sol–gel-derived carbon ceramic electrode for hydrogen evolution reaction

Various Au–Pd bimetallic nanoparticles were electrodeposited on microwave irradiated carbon ceramic electrodes (MWCCE). Au:Pd molar ratios of 75:25, 50:50 and 25:75 were electrodeposited on MWCCE and their electrocatalytic activities for hydrogen evolution reaction (HER) were evaluated. Among them, the alloy with Au:Pd molar ratio of 25:75 showed highest electrocatalytic activity for HER. The structure and nature of these alloys were characterized by scanning electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, inductively coupled plasma, and cyclic voltammetry. Alloying degree of bimetallic nanoparticles and electrodeposition time were optimized. The electrocatalytic activity of bimetallic nanoparticles was also compared with individual non-alloyed Au and Pd catalysts and the results showed that alloy nanoparticles have higher electrocatalytic activity for hydrogen evolution. The Tafel slopes ranges are obtained from 136 mV dec−1 to 165 mV dec−1 for HER on bare and modified MWCCE and kinetic parameters show that the Volmer step must control the HER. The stability of the best electrode is determined by chronopotentiometric and it showed a good stability.

Electrocatalytic evolution of hydrogen on the NiCu/Al2O3/nano-carbon network composite electrode

We present a way to fabricate the NiCu/Al2O3/nano-carbon network (NCN) composite electrode by coelectrodepositing NiCu particles, using a novel conductive alumina/NCN composite material as the support. The morphology, crystalline phases, and compositions are characterized by field-emission scanning electron microscope, energy dispersive X-ray spectroscope, X-ray diffraction, and Raman spectroscopy. The electrocatalytic behaviors of this NiCu/Al2O3/NCN composite material for hydrogen evolution reaction (HER) in alkaline solution are studied by cathodic polarization curves, electrochemical impedance spectroscopy (EIS), and chronoamperometry. The results show that nickel–copper particles are briefly deposited and uniformly distributed over the carbon layer of the conductive ceramics between alumina grains, in the form of a NiCu solid solution with face-centered cubic structure. The NiCu/Al2O3/NCN composite displays a high electrochemical stability in alkaline solution and relatively high electrocatalytic activity for HER due to its relatively high real surface area and high intrinsic electrocatalytic effect of NiCu alloy particles. The associated kinetic parameters of HER are systematically investigated using EIS.

NiW/TiO x composite layers as cathode material for hydrogen evolution reaction

NiW + TiO x composite layers were obtained in electrolyte solutions containing nickel sulphamate with high concentration of W and nonstoichiometric titanium oxides particles (TiO x ). The co-deposition of NiW layers with TiO x particles was carried out under potentiostatic conditions on pristine and oxidized carbon fibers by stirring. Comparatively, NiW layers were obtained under the same experimental conditions. The morphology of the deposits was examined by means of scanning electron microscopy (SEM). Secondary crystallization of NiW layers on the surface of the embedded Ti oxides particles was observed. The structure and the chemical states of the elements in the deposits were illustrated by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) respectively. Electrochemical impedance spectroscopy (EIS) was used to study the electrocatalytic activity of these materials for the hydrogen evolution reaction (HER) in acid solution. The results showed that NiW + TiO x layers on oxidized carbon fiber electrodes possess the highest electrocatalytic activity for HER compared with NiW + TiO x layers on nonoxidized carbon fiber electrodes and NiW layers on oxidized carbon fiber electrodes.