Hydrogen Evolution Reaction In Alkaline Electrolyte Research Articles

Pd doped Ni derived from Ni - Metal organic framework for efficient hydrogen evolution reaction in alkaline electrolyte

The poor conductivity of metal-organic frameworks (MOFs) has greatly restricted their widespread application in water splitting. Herein, the Ni-MOF is used to be a precursor to support a stable three-dimensional structure, high surface areas and to prepare various contents of Pd doped Ni alloys (Pd/Ni-1, Pd/Ni-2 and Pd/Ni-3). The hydrogen evolution reaction (HER) activity of samples is compared in alkaline electrolyte (1.0 M KOH). As-prepared catalysts exhibit uniform dispersion, good crystallinity, high purity and a small particle size according to the physical characterization. What is more, based on the electrochemical characterization, Pd/Ni-3 has an exclellent HER performances with a lower overpotential (50 mV in base at 10 mA·cm−2), smaller Tafel slope (102 mV·dec−1) and more positive initial potential (ƞ at 1 mA·cm−2; Δ ƞ = 660 mV) than that of Ni-MOF. The reduction percentage of resistance charge transfer (Rct) relative to Ni-MOF of Pd/Ni-3 is up to 95.6%. This work may offer guidance to make up the low conductivity of MOF for HER in alkaline electrolyte.

Co2P/CoP hybrid as a reversible electrocatalyst for hydrogen oxidation/evolution reactions in alkaline medium

Due to the rapid development of alkaline polymer electrolyte fuel cells and water splitting, it is becoming increasingly urgent to develop non-precious metal electrocatalysts for the hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER) in alkaline medium. Herein, Co2P/CoP hybrid is synthesized from cobalt carbonate hydroxide (CoCH) precursor, and further evaluated for the electrocatalytic HOR and HER in alkaline electrolytes. Specifically, benefiting from the reasonable hybrid structure that integrate suitable hydrogen adsorption energy of CoP and excellent conductivity of Co2P, Co2P/CoP hybrid exhibits excellent catalytic activities. The Co2P/CoP@NF hybrid has impressive HER activity, with a current density of −10 mA cm−2 at the overpotentials of −61 mV and the Tafel slope of 55.1 mV dec−1, which can compete with recently reported transition metal phosphides and cobalt-based catalysts. In addition, the exchange current density of Co2P/CoP@NF hybrid is ~ 0.82 mA cm−2 for HOR, which is close to commercial Pt/C catalyst (~1.14 mA cm−2).

Potentiostatic electrodeposition of Ni–Se–Cu on nickel foam as an electrocatalyst for hydrogen evolution reaction

Development of cost-effective and efficient earth-abundant catalysts for hydrogen evolution reaction (HER) is a great challenge. In this study, by one-step potentiostatic electrodeposition, the Ni–Se–Cu electrocatalyst on nickel foam was fabricated as a binder-free HER electrocatalyst. As compared with Ni–Se electrocatalysts, such fabricated Ni–Se–Cu electrocatalyst exhibited prominent electrocatalytic activity to the HER in alkaline electrolyte. This Ni–Se–Cu electrocatalyst exhibits a small overpotential of 136 mV to achieve a current density of 10 mA·cm−2 and high electrochemical stability. The remarkable HER properties of Ni–Se–Cu electrocatalyst mainly originate from high electronic conductivity induced by Cu-doping. This work shows a cheap and simple avenue to develop high efficient non-noble electrochemical electrocatalysts for HER.

Highly disordered cobalt oxide nanostructure induced by sulfur incorporation for efficient overall water splitting

Exploitation of cost-efficient active electrocatalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) plays a significant role for scalable electricity-to-hydrogen energy conversion. Crystalline transition metal oxides as the promising non-noble catalysts, however, are often suffering from the large excess overpotential and unsatisfactory performance. To boost their intrinsic catalytic property, we report here an incorporation of electronegative sulfur into crystalline cobalt oxide (S-CoO x ) to create structural disorder via a facile room-temperature ion exchange strategy. Compared with its crystalline form, the disorder in S-CoO x catalyst enables the increased low oxygen coordination and rich defect sites, which endows S-CoO x a superior catalytic activity for both OER and HER in alkali. Intriguingly, a water electrolyser adopting S-CoO x as both OER and HER electrode catalysts requires mere 1.63 V to reach a current density of 10 mA cm −2 in 1 M KOH. This work highlights the effectiveness of designing high-performing electrocatalysts for water electrolysers based on disordered structural materials. • The structurally disordered S-CoO x catalyst was synthesized via a facile room-temperature sulfur ion exchange strategy. • The structurally disordered catalyst shows increased low oxygen coordination and more defect sites. • Experimental and DFT calculation results reveal that a preferable electronic state was generated for the disorderedS-CoO x catalyst. • This novel structurally disordered strategy enables the S-CoO x catalyst a superior catalytic activity for both OER and HER in alkaline electrolyte.

Ni3S2 in Situ Grown on Ni Foam Coupled with Nitrogen-Doped Carbon Nanotubes as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction in Alkaline Solution.

Searching for a highly efficient electrocatalyst for the hydrogen evolution reaction (HER) in alkaline solution is still challenging. In this work, we report a HER electrocatalyst composed of Ni foam, Ni3S2, and nitrogen-doped carbon nanotubes (NF@Ni3S2@NCNTs). The good lattice matching between Ni and Ni3S2, interstitial doping of C and N atoms, and synergistic effect of NCNTs make NF@Ni3S2@NCNTs highly efficient HER electrocatalysts in alkaline solution. NF@Ni3S2@NCNTs exhibit an overpotential of 93.89 mV at a current density of 10 mA cm–2, a Tafel slope of 54 mV dec–1, and superior stability for HER in 1 M KOH solution. Our findings will promote the reasonable design and synthesis of an efficient electrocatalyst for HER in alkaline electrolytes.

Metallic molybdenum sulfide nanodots as platinum-alternative co-catalysts for photocatalytic hydrogen evolution

Molybdenum sulfide (MoS2) has attracted considerable attention as one of noble-metal-free co-catalysts of hydrogen evolution reaction (HER) for artificial photosynthetic water splitting. There are well-known challenges in optimizing its catalytic activity to pursue the replacement of platinum (Pt) for HER, owing to the edge-limited active sites and intrinsically poor conductivity. Herein, we prepared metallic MoS2 nanodots (MNDs) with 1T-phase occupation and edge-exposure maximum to achieve the simultaneous optimization of electric conductivity and active sites. When integrated as co-catalysts with graphitic carbon nitride (g-CN) for sunlight-driven HER in alkaline electrolyte, the outstanding photocatalytic activity with hydrogen evolution rate of 5.62 mmol g−1 h−1, over 280 times higher than that of pure g-CN, demonstrates the excellent co-catalytic performance of 1T-MoS2 NDs (1T-MNDs) that even comparable to state-of-the-art Pt. The photo-induced charge dynamics describe the role of 1T-MNDs in facilitating charge separation as well as surface catalytic reaction, suggesting a promising potential of 1T-MNDs with more active sites and higher conductivity as Pt-alternative co-catalysts for solar hydrogen production.

Ni Nanoparticles on Ultrathin Mo2C Interconnected Nanonet: An Efficient 3D Hydrogen-Evolving Electrocatalyst with Superior Durability

Exploring efficient non-noble-metal electrocatalysts for hydrogen evolution reaction (HER) is becoming an urgent task owning to the persistently aggravating energy crisis. Herein, small Ni nanoparticles embedded in ultrathin Mo2C interconnected nanonet on carbon nanofibers (CF) were prepared for the first time. The Ni/Mo2C nanonet on CF (Ni/Mo2C/CF) carbonized under 650°C exhibits ultra-high catalytic activity which only needs 92 mV to afford 10 A/g with remarkable durability for HER in alkaline electrolyte.

δ-MnO2 nanoflowers on sulfonated graphene sheets for stable oxygen reduction and hydrogen evolution reaction

Nanoflowers are highly beneficial structural features for improving catalysis on transitional metal-based materials with regarded to the electrocatalytic activity, cost effectiveness and durability. In this study, the manganese dioxide nanoflowers onto sulfonated graphene sheets (denoted as δ-MnO2/SGS) is synthesized by a simple hydrothermal method for bifunctional electrocatalytic application in oxygen reduction reaction (ORR) and hydrogen evolution reaction (HER). The formation of δ-MnO2 nanoflowers onto SGS plays a crucial role in intrinsic catalytic activity, resulting in an impressive enhancement in both ORR and HER in alkaline electrolyte. The morphological features and X-ray analysis are shown the successful sulfonation and the Mn presents in oxide form with δ-type crystallographic structure. The growth reaction mechanism of δ-MnO2 nanoflowers is proposed in alkaline media. The robust electrocatalysis is inherited from the cave among crystalline lego-block-like petals at microscale level and the large interlayer spacing at nanoscale level of δ-MnO2 nanoflowers with significant electrical conductivity. The δ-MnO2/SGS catalyst exhibits nearly same ORR and HER activity in terms of current density with electron transfer and final current density with Tafel slope, respectively, compare to the benchmark Pt/C.

(Fe0.2Ni0.8)0.96S tubular spheres supported on Ni foam as an efficient bifunctional electrocatalyst for overall water splitting

Earth-abundant and efficient bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are highly significant for renewable energy systems. However, the performance of existing electrocatalysts is usually restricted by the low electroic conductivity and the limited amount of exposed active sites. In this work, (Fe0.2Ni0.8)0.96S tubular spheres supported on Ni foam have been prepared by a sulfuration of FeNi layered double hydroxide spheres grown on Ni foam. Benefiting from the unique tubular sphere architecture, the rich inner defects and the enhanced electron interactions between Fe, Ni and S, this electrocatalyst shows low overpotential of 48 mV for HER at 10 mA cm−2 in 1.0 mol L−1 KOH solution, which is one of the lowest value of non-previous electrocatalyts for HER in alkaline electrolyte. Furthermore, assembled this versatile electrode as an alkaline electrolyzer for overall water splitting, a current density of 10 mA cm−2 is achieved at a low cell voltage of 1.56 V, and reach up to 30 mA cm−2 only at an operating cell voltage of 1.65 V.

Hydrogen Evolution Reaction in Alkaline Media: Alpha- or Beta-Nickel Hydroxide on the Surface of Platinum?

Reducing the energy consumption of a hydrogen evolution reaction (HER) at a platinum (Pt) electrode is important for the hydrogen economy. Herein, we report the loading of alpha- or beta-nickel hydroxide (α- or β-Ni(OH)2) nanostructures on the surface of a Pt electrode to improve its catalytic activity and stability for HER in alkaline electrolytes. Both experimental and theoretical studies reveal that β-Ni(OH)2 is a better co-catalyst of Pt than α-Ni(OH)2 for promoting the HER, attributed to the higher water dissociation ability of β-Ni(OH)2, as well as the stronger interactions between β-Ni(OH)2 and the Pt electrode. Particularly, the overpotential of the HER in 0.1 M KOH at 10 mA cm–2 is decreased from 278 mV at the Pt electrode to 92 mV at the β-Ni(OH)2/Pt electrode, and the Tafel slope decreased from 62 to 42 mV dec–1, correspondingly. The performance of the β-Ni(OH)2/Pt catalytic electrode surpasses that of most of the previously reported electrodes for the same purpose.

Nickel Hydr(oxy)oxide Nanoparticles on Metallic MoS2 Nanosheets: A Synergistic Electrocatalyst for Hydrogen Evolution Reaction.

Molybdenum disulfide (MoS2)‐based materials have been recently identified as promising electrocatalysts for hydrogen evolution reaction (HER). However, little work has been done to improve the catalytic performance of MoS2 toward HER in alkaline electrolytes, which is more suitable for water splitting in large‐scale applications. Here, it is reported that the hybridization of 0D nickel hydr(oxy)oxide nanoparticles with 2D metallic MoS2 nanosheets can significantly enhance the HER activities in alkaline and neutral electrolytes. Impressively, the optimized hybrid catalyst can drive a cathodic current density of 10 mA cm−2 at an overpotential of ≈73 mV for HER in 1 m KOH, about 185 mV smaller than the original MoS2. The improved HER activity is attributed to a bifunctional mechanism adopted in these hybrid catalysts, in which nickel hydr(oxy)oxide promotes the water adsorption and dissociation to supply protons for subsequent reactions occurred on MoS2 to generate H2.

Fiber-shaped Supercapacitor and Electrocatalyst Containing of Multiple Carbon Nanotube Yarns and One Platinum Wire

Light weight and flexible fiber-shaped supercapacitors (FSSCs) that are considered to be ideal energy storage devices for powering wearable electronics. A flexible, high energy density all-solid-state Pt/n-CNT@PANI FSSCs was fabricated by using a simple method. The electrode was formed by twisting a number of CNT yarns (n) with one platinum filament as current collector, upon which PANI nanowires were deposited in-situ to form the final Pt/n-CNT@PANI FSSCs. The electrode structure with n=5 fabricated at a twist level of 1000T/m showed the best electrochemical performance. The optimum flexible Pt/5-CNT@PANI FSSC exhibited a specific capacitance of 217.7F/g at the current density of 0.2A/g, indicating a 7-fold increase in specific capacitance than the initial Pt/1-CNT@PANI with one CNT yarn (n=1) of about 29.9F/g. The Pt/5-CNT@PANI FSSC showed an energy density of 30.22Wh/kg accompanied by a power density of 91.88W/kg. The Pt/5-CNT@PANI exhibits remarkable electrocatalytic activity for hydrogen evolution reaction (HER) with a low onset overpotential of −188mV and low Tafel slope of 84.99mV/dec. The Pt/5-CNT@PANI yarns can be used as not only FSSC with excellent cycle stability and flexibility and but also an active and stable electrocatalyst for HER in alkaline electrolytes.