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Journal ArticleDOI: 10.1021/ACSAMI.0C22409

Impact of Surface Hydrophilicity on Electrochemical Water Splitting

02 Mar 2021-ACS Applied Materials & Interfaces (American Chemical Society (ACS))-Vol. 13, Iss: 10, pp 11940-11947
Abstract: The activity of electrocatalysts can be improved by modifying their electronic structures and surface morphologies. In electrochemical reactions with gas evolution, the performance of an electrocatalyst is also affected by how easily gas bubbles depart from an electrocatalyst surface. However, it is difficult to quantitatively estimate the improvement in the performance that can be achieved by promoting the departure of gas bubbles from the electrocatalyst surface. This study investigated the effect of surface hydrophilicity on the hydrogen evolution reaction (HER). The water contact angles of the nickel phosphorous (NiP) films were controlled from 40.3 to 77.2° with imperceptible differences in their intrinsic electronic structures and surface areas. Electrochemical analyses and in situ visualization of the gas evolution on the NiP films indicated that an increase in the hydrophilicity of the electrocatalysts reduced the size of gas bubbles formed on the NiP films and shortened the duration of the bubbles' stay on the NiP surface. A faster gas departure enabled continuous participation of the electrocatalyst surface in hydrogen evolution, leading to a stable electrochemical behavior of the electrocatalyst and a decrease in the overpotential at a given current density. A full-cell test revealed that the enhancement of hydrogen bubble departure on a hydrophilic NiP surface with a contact angle of 40.3° reduced the overpotential by 134 mV at a current density of 100 mA/cm2 compared to a more hydrophobic film with a contact angle of 77.2°.

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Topics: Electrocatalyst (63%), Gas evolution reaction (55%), Overpotential (55%) ... show more
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6 results found


Journal ArticleDOI: 10.1016/J.JALLCOM.2021.162409
Iqbal Ahmad1, Iqbal Ahmad2, Jawad Ahmed1, Saima Batool3  +11 moreInstitutions (11)
Abstract: The production of an inexpensive, highly active electrocatalyst for a simple oxygen evolution reaction (OER) based on earth-abundant transition metals is still a major challenge. In addition, the ambiguity of the water splitting reaction (hydrogen evolution and OER) is a hurdle in the manufacture of suitable catalysts for the efficient water electrolysis process. Here, the synthesis of iron oxide/iron phosphide (Fe2O3/FeP) heterostructure and its counterparts Fe2O3 and FeP as cheap electrocatalysts for water electrolysis is presented. Characterization techniques such as powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy were used to analyze the structure of these electrocatalysts. Heterostructure Fe2O3/FeP has been shown to be a more active electrocatalyst than its counterparts. It initiates OER at a remarkably low potential of 1.49 V vs. reverse hydrogen electrode (RHE). For this electrocatalyst, a current density of 10 mA/cm2 is achieved at an overpotential of 264 mV for OER in 1.0 M potassium hydroxide solution and the value of the Tafel slope is 47 mV dec−1, outperforming its complements (Fe2O3 and FeP) under similar conditions. The results obtained are superior to those of previously reported Fe-based OER electrocatalysts. The Fe2O3/FeP electrocatalyst has proven its long-term stability by driving OER at 1.65 V (vs. RHE) for about 12.5 h.

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Topics: Electrocatalyst (59%), Electrolysis of water (55%), Water splitting (54%) ... show more

Open accessJournal ArticleDOI: 10.3389/FCHEM.2021.700020
Jie Ying1, Huan Wang1Institutions (1)
Abstract: Electrochemical water splitting involving hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is a greatly promising technology to generate sustainable and renewable energy resources, which relies on the exploration regarding the design of electrocatalysts with high efficiency, high stability, and low cost. Transition metal phosphides (TMPs), as nonprecious metallic electrocatalysts, have been extensively investigated and proved to be high-efficient electrocatalysts in both HER and OER. In this minireview, a general overview of recent progress in developing high-performance TMP electrocatalysts for electrochemical water splitting has been presented. Design strategies including composition engineering by element doping, hybridization, and tuning the molar ratio, structure engineering by porous structures, nanoarray structures, and amorphous structures, and surface/interface engineering by tuning surface wetting states, facet control, and novel substrate are summarized. Key scientific problems and prospective research directions are also briefly discussed.

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Topics: Water splitting (53%)

Journal ArticleDOI: 10.1016/J.IJHYDENE.2021.08.233
S. Swathi1, Rathinam Yuvakkumar1, P. Senthilkumar2, Ganesan Ravi1  +1 moreInstitutions (3)
Abstract: Highly proficient, long-lasting non-noble-metal-supported electrocatalysts for hydrogen evolution reaction are important for hydrogen energy production through alkaline electrolyte. In transition metal dichalcogenides, tungsten sulfide is one of the popular materials and is used in a wide variety of applications. In this work, pristine and cationic surfactant assisted tungsten sulfide were successfully synthesized via simple hydrothermal method in alkaline electrolyte for hydrogen evolution reaction. X-ray diffraction confirmed tungsten sulfide rhombohedral structure formation with high index plane (003). Scanning electron microscopy explored tungsten sulfide nanosheet-assembled mesoporous sphere morphology. Tungsten sulfide and cationic surfactant assisted tungsten sulfide overpotential values were found to be 141 and 102 mV at 10 mA/cm2 from linear sweep voltammetry curves. The obtained Tafel slope of tungsten sulfide and cationic surfactant assisted tungsten sulfide were 26.9 and 21.4 mV/dec, respectively. The solution and charge transfer resistance of the prepared materials were obtained from Nyquist plot and found to be 1.7 and 1.4 Ω, and 53.6 and 32 Ω, respectively. The specific surface area, pore diameter, and volume were analyzed by Brunauer–Emmett–Teller method and obtained values for surface area, pore size, and volume of cetyltrimethylammonium bromide assisted tungsten sulfide were 65.05 m2/g, 3.502 nm, and 0.067 cc/g, respectively. The obtained result suggested that 0.1 M cationic surfactant assisted tungsten sulfide showed high catalytic activity with minimum overpotential. Long-term durability studies also suggested that the optimized surfactant-assisted tungsten sulfide had excellent stability over a prolong time of 16 h without any decay. However, the stability of the material exhibited only 90% retention which will improve in our near future works by using carbon-based materials. Hence, carbon-based materials exhibited outstanding chemical stability and offer large surface area, which significantly improves the hydrogen evolution reaction activity and suggests to be used in large-scale applications.

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Topics: Sulfide (68%), Tungsten (61%), Overpotential (54%) ... show more

Journal ArticleDOI: 10.1039/D1DT02194J
Kaili Wang1, Xiujuan Sun1, Wen Huang1, Qiuhan Cao1  +5 moreInstitutions (2)
Abstract: Nickel cyclotetraphosphate grown on carbon cloth (Ni2P4O12/CC) is synthesized via an anion exchange reaction method and it shows excellent hydrogen evolution reaction (HER) activity and strong working stability in acid due to the merits of its unique polymer-like structure, mesoporous characteristics, and superhydrophilic surface.

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Topics: Nickel (53%), Mesoporous material (52%)

Journal ArticleDOI: 10.1002/ANIE.202107886
Jianan Li1, Jili Li2, Tao Liu2, Lin Chen2  +6 moreInstitutions (2)
22 Oct 2021-Angewandte Chemie
Abstract: Urea electrolysis is a prospective technology for simultaneous H2 production and nitrogen suppression in the process of water being used for energy production. Its sustainability is currently founded on innocuous N2 products; however, we discovered that prevalent nickel-based catalysts could generally over-oxidize urea into NO2- products with ≈80 % Faradaic efficiencies, posing potential secondary hazards to the environment. Trace amounts of over-oxidized NO3- and N2 O were also detected. Using 15 N isotopes and urea analogues, we derived a nitrogen-fate network involving a NO2- -formation pathway via OH- -assisted C-N cleavage and two N2 -formation pathways via intra- and intermolecular coupling. DFT calculations confirmed that C-N cleavage is energetically more favorable. Inspired by the mechanism, a polyaniline-coating strategy was developed to locally enrich urea for increasing N2 production by a factor of two. These findings provide complementary insights into the nitrogen fate in water-energy nexus systems.

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Topics: Urea (52%)

References
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44 results found


Journal ArticleDOI: 10.1038/NATURE11475
Steven Chu1, Arun Majumdar1Institutions (1)
16 Aug 2012-Nature
Abstract: Access to clean, affordable and reliable energy has been a cornerstone of the world's increasing prosperity and economic growth since the beginning of the industrial revolution. Our use of energy in the twenty–first century must also be sustainable. Solar and water–based energy generation, and engineering of microbes to produce biofuels are a few examples of the alternatives. This Perspective puts these opportunities into a larger context by relating them to a number of aspects in the transportation and electricity generation sectors. It also provides a snapshot of the current energy landscape and discusses several research and development opportunities and pathways that could lead to a prosperous, sustainable and secure energy future for the world.

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Topics: Energy policy (61%), Energy source (60%), Energy development (60%) ... show more

5,397 Citations


Journal ArticleDOI: 10.1149/1.1856988
Abstract: Department of Physics, Technical University Munich, D-85748 Garching, GermanyA density functional theory database of hydrogen chemisorption energies on close packed surfaces of a number of transition andnoble metals is presented. The bond energies are used to understand the trends in the exchange current for hydrogen evolution. Avolcano curve is obtained when measured exchange currents are plotted as a function of the calculated hydrogen adsorptionenergies and a simple kinetic model is developed to understand the origin of the volcano. The volcano curve is also consistent withPt being the most efficient electrocatalyst for hydrogen evolution.© 2005 The Electrochemical Society. @DOI: 10.1149/1.1856988# All rights reserved.Manuscript submitted May 10, 2004; revised manuscript received August 12, 2004. Available electronically January 24, 2005.

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Topics: Hydrogen (51%)

2,623 Citations


Open accessJournal ArticleDOI: 10.1021/JA403440E
Abstract: Nanoparticles of nickel phosphide (Ni2P) have been investigated for electrocatalytic activity and stability for the hydrogen evolution reaction (HER) in acidic solutions, under which proton exchange membrane-based electrolysis is operational. The catalytically active Ni2P nanoparticles were hollow and faceted to expose a high density of the Ni2P(001) surface, which has previously been predicted based on theory to be an active HER catalyst. The Ni2P nanoparticles had among the highest HER activity of any non-noble metal electrocatalyst reported to date, producing H2(g) with nearly quantitative faradaic yield, while also affording stability in aqueous acidic media.

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Topics: Electrocatalyst (64%), Phosphide (56%), Catalysis (53%) ... show more

2,156 Citations


Journal ArticleDOI: 10.1038/NMAT3313
Ram Subbaraman1, Dusan Tripkovic1, Kee-Chul Chang1, Dusan Strmcnik1  +6 moreInstitutions (1)
01 Jun 2012-Nature Materials
Abstract: Design and synthesis of materials for efficient electrochemical transformation of water to molecular hydrogen and of hydroxyl ions to oxygen in alkaline environments is of paramount importance in reducing energy losses in water–alkali electrolysers. Here, using 3d-M hydr(oxy)oxides, with distinct stoichiometries and morphologies in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) regions, we establish the overall catalytic activities for these reaction as a function of a more fundamental property, a descriptor, OH–M2+δ bond strength (0 ≤ δ ≤ 1.5). This relationship exhibits trends in reactivity (Mn < Fe < Co < Ni), which is governed by the strength of the OH–M2+δ energetic (Ni < Co < Fe < Mn). These trends are found to be independent of the source of the OH, either the supporting electrolyte (for the OER) or the water dissociation product (for the HER). The successful identification of these electrocatalytic trends provides the foundation for rational design of ‘active sites’ for practical alkaline HER and OER electrocatalysts. Efficient electrochemical transformation of water to molecular hydrogen and of hydroxyl ions to oxygen in alkaline environments is important for reducing energy losses in water–alkali electrolysers. Insight into the activities of hydr(oxy)oxides on platinum catalyst surfaces for hydrogen and oxygen evolution reactions should prove significant for designing practical alkaline electrocatalysts.

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Topics: Oxygen evolution (57%), Catalysis (53%), Electrocatalyst (53%) ... show more

1,728 Citations


Journal ArticleDOI: 10.1038/S41570-016-0003
11 Jan 2017-
Abstract: Sunlight is by far the most plentiful renewable energy resource, providing Earth with enough power to meet all of humanity's needs several hundred times over. However, it is both diffuse and intermittent, which presents problems regarding how best to harvest this energy and store it for times when the sun is not shining. Devices that use sunlight to split water into hydrogen and oxygen could be one solution to these problems, because hydrogen is an excellent fuel. However, if such devices are to become widely adopted, they must be cheap to produce and operate. Therefore, the development of electrocatalysts for water splitting that comprise only inexpensive, earth-abundant elements is critical. In this Review, we investigate progress towards such electrocatalysts, with special emphasis on how they might be incorporated into photoelectrocatalytic water-splitting systems and the challenges that remain in developing these devices. Splitting water is an attractive means by which energy — either electrical and/or light — is stored and consumed on demand. Active and efficient catalysts for anodic and cathodic reactions often require precious metals. This Review covers base-metal catalysts that can afford high performance in a more sustainable and available manner.

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Topics: Water splitting (51%)

1,686 Citations