Open accessJournal Article

Graphene/MoS2/FeCoNi(OH)x and Graphene/MoS2/FeCoNiPx multilayer-stacked vertical nanosheets on carbon fibers for highly efficient overall water splitting

02 Mar 2021-Nature Communications (Nature Publishing Group)-Vol. 12, Iss: 1, pp 1380-1380
Abstract: Development of excellent and cheap electrocatalysts for water electrolysis is of great significance for application of hydrogen energy. Here, we show a highly efficient and stable oxygen evolution reaction (OER) catalyst with multilayer-stacked hybrid structure, in which vertical graphene nanosheets (VGSs), MoS2 nanosheets, and layered FeCoNi hydroxides (FeCoNi(OH)x) are successively grown on carbon fibers (CF/VGSs/MoS2/FeCoNi(OH)x). The catalyst exhibits excellent OER performance with a low overpotential of 225 and 241 mV to attain 500 and 1000 mA cm−2 and small Tafel slope of 29.2 mV dec−1. Theoretical calculation indicates that compositing of FeCoNi(OH)x with MoS2 could generate favorable electronic structure and decrease the OER overpotential, promoting the electrocatalytic activity. An alkaline water electrolyzer is established using CF/VGSs/MoS2/FeCoNi(OH)x anode for overall water splitting, which generates a current density of 100 mA cm−2 at 1.59 V with excellent stability over 100 h. Our highly efficient catalysts have great prospect for water electrolysis. While water-splitting electrocatalysis offers a renewable means for carbon-neutral energy production, it is a challenge to design efficient, active, and stable catalysts. Here, authors prepare multilayer composite nanosheet materials as bifunctional water-splitting electrocatalysts.

Topics: , Water splitting (55%), Overpotential (54%) ... read more
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23 results found

Journal Article
Shuo Geng1, Fenyang Tian1, Menggang Li1, Yequn Liu2  +4 moreInstitutions (3)
02 Aug 2021-Nano Research
Abstract: The hydrogen evolution reaction (HER) of molybdenum disulfide (MoS2) is limited in alkaline and acid solution because the active sites are on the finite edge with extended basal plane remaining inert. Herein, we activated the interfacial S sites by coupling with Ru nanoparticles on the inert basal plane of MoS2 nanosheets. The density functional theory (DFT) calculation and experimental results show that the interfacial S electronic structure was modulated. And the results of ΔGH* demonstrate that the adsorption of H on the MoS2 was also optimized. With the advantage of interfacial S sites activation, the Ru-MoS2 needs only overpotential of 110 and 98 mV to achieve 10 mA·cm−2 in both 0.5 M H2SO4 and 1 M KOH solution, respectively. This strategy paves a new way for activating the basal plane of other transition metal sulfide electrocatalysts for improving the HER performance.

Topics: Overpotential (53%), Molybdenum disulfide (51%)

7 Citations

Journal Article
Shasha Li1, Enze Li2, Xiaowei An3, Xiaowei An4  +3 moreInstitutions (5)
05 Aug 2021-Nanoscale
Abstract: As a clean energy carrier, hydrogen has priority in decarbonization to build sustainable and carbon-neutral economies due to its high energy density and no pollutant emission upon combustion. Electrochemical water splitting driven by renewable electricity to produce green hydrogen with high-purity has been considered to be a promising technology. Unfortunately, the reaction of water electrolysis always requires a large excess potential, let alone the large-scale application (e.g., >500 mA cm−2 needs a cell voltage range of 1.8–2.4 V). Thus, developing cost-effective and robust transition metal electrocatalysts working at high current density is imperative and urgent for industrial electrocatalytic water splitting. In this review, the strategies and requirements for the design of self-supported electrocatalysts are summarized and discussed. Subsequently, the fundamental mechanisms of water electrolysis (OER or HER) are analyzed, and the required important evaluation parameters, relevant testing conditions and potential conversion in exploring electrocatalysts working at high current density are also introduced. Specifically, recent progress in the engineering of self-supported transition metal-based electrocatalysts for either HER or OER, as well as overall water splitting (OWS), including oxides, hydroxides, phosphides, sulfides, nitrides and alloys applied in the alkaline electrolyte at large current density condition is highlighted in detail, focusing on current advances in the nanostructure design, controllable fabrication and mechanistic understanding for enhancing the electrocatalytic performance. Finally, remaining challenges and outlooks for constructing self-supported transition metal electrocatalysts working at large current density are proposed. It is expected to give guidance and inspiration to rationally design and prepare these electrocatalysts for practical applications, and thus further promote the practical production of hydrogen via electrochemical water splitting.

Topics: , Water splitting (56%)

4 Citations

Journal Article
Yun Tong1, Pengzuo Chen2Institutions (2)
Abstract: Rational design of non-noble metal electrocatalysts with high intrinsic activity for both the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is extremely impressive for sustainable electrocatalytic water splitting systems. However, it still remains a major challenge to engineer bifunctional performance. Here, we put forward a highly efficient water electrolyzer based on Ni3S2-based materials. The hierarchical structure of Ni3S2 can be well regulated for optimizing the HER catalytic activity. The best c-Ni3S2/NF electrode exhibits a much smaller overpotential of 220 mV to reach the current density of 100 mA cm−2. Upon introducing Fe species onto the Ni3S2/NF electrode by a simple dipping/drying method, the intrinsic OER activity can be extremely improved. As a result, the Fe-c-Ni3S2/NF catalyst showed excellent catalytic activity for the OER, including an overpotential of 193 mV at 10 mA cm−2, high specific current density and excellent stability. Post-characterization studies proved that the remaining S anions have an effective influence on improving the OER intrinsic activity. The assembled water electrolyzer also presented superior performance, such as a very low cell voltage of 1.50 V at 10 mA cm−2 and excellent durability for 120 h in alkaline medium. This strategy provides a promising way to design highly active and low-cost materials for overall water electrolysis.

Topics: , Overpotential (57%), Water splitting (55%) ... read more

3 Citations

Journal Article
Wen-Yi Huo1, Shiqi Wang2, Wen-Han Zhu1, Zeling Zhang2  +4 moreInstitutions (3)
01 Jun 2021-
Abstract: Advanced materials for electrocatalytic water splitting applications have been sought-after considering both environmental and economic requirements. However, the traditional materials design concept limits the exploration of high-performance catalysts. The born of a materials design concept based on multiple elements, high-entropy materials, provides a promising path to break the shackles of compositional design in materials science. A number of high-entropy materials were reported to show remarkable properties for electrocatalytic water splitting applications. High-entropy materials were widely confirmed to be one kind of the best electrocatalysts for water splitting applications. Due to the synergy of multiple metal components, they show excellent catalytic activity. Several nontraditional methods were developed and reported to prepare high-performance high-entropy materials. This review article presents the recent progress on high-entropy materials for electrocatalytic water splitting applications. Moreover, it presents the research interests and future prospects in this field.

2 Citations

Journal Article
Xiaogang Chen1, Xuan Zhao1, Yuanyuan Wang1, Shanshan Wang1  +4 moreInstitutions (1)
20 Aug 2021-Chemcatchem
Abstract: In recent years, the catalyst efficiency of hydrogen evolution reaction (HER) has been extensively studied. However, the stability of catalysts at high current densities is still a challenge. Herein, layered Ni−Co−P was electrodeposited on carbon fiber paper (CFP) via cyclic voltammetry (CV). This low‐cost electrode exhibits high efficiency and excellent durability for HER in 1 M KOH. To achieve current densities of 10, 100, 500, and 1000 mA cm−2, Ni−Co−P/CFP required overpotentials of 49, 95, 170, and 295 mV, respectively. The layered structure allows the catalyst to fall off layer by layer. After the outer layer of catalyst falls off, the inner layer of catalyst will be exposed to continue working. After 300 h of HER at 1000 mA cm−2, Ni−Co−P/CFP still has a regular morphology and high efficiency. Our work shows that layered Ni−Co−P/CFP has excellent prospects for practical applications.

Topics: Water splitting (61%), Electrode (50%)

1 Citations

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66 results found

Journal Article
Abstract: Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. [S0031-9007(96)01479-2] PACS numbers: 71.15.Mb, 71.45.Gm Kohn-Sham density functional theory [1,2] is widely used for self-consistent-field electronic structure calculations of the ground-state properties of atoms, molecules, and solids. In this theory, only the exchange-correlation energy EXC › EX 1 EC as a functional of the electron spin densities n"srd and n#srd must be approximated. The most popular functionals have a form appropriate for slowly varying densities: the local spin density (LSD) approximation Z d 3 rn e unif

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117,932 Citations

Journal Article
Georg Kresse1, Daniel P. Joubert2Institutions (2)
15 Jan 1999-Physical Review B
Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.

Topics: Cauchy stress tensor (53%)

46,297 Citations

Journal Article
Chaoliang Tan1, Xiehong Cao2, Xiehong Cao1, Xue-Jun Wu1  +9 moreInstitutions (2)
17 Mar 2017-Chemical Reviews
Abstract: Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

2,618 Citations

Journal Article
15 Aug 1977-Physical Review B
Abstract: The efficiency of two different methods for obtaining "special" points useful for Brillouin-zone integrations of periodic functions is compared. We find that for some Bravais lattices (such as body-centered cubic and hexagonal), the method suggested by Monkhorst and Pack leads to different and sometimes less efficient point sets than those previously obtained by Chadi and Cohen. For a two-dimensional oblique lattice, special points twice as efficient as those suggested by Cunningham are given.

Topics: Bravais lattice (67%), Brillouin zone (66%), Lattice (music) (56%)

2,358 Citations

Open accessJournal Article
Abstract: A detailed investigation has been carried out of the structure and electrochemical activity of electrodeposited Ni-Fe films for the oxygen evolution reaction (OER) in alkaline electrolytes. Ni-Fe films with a bulk and surface composition of 40% Fe exhibit OER activities that are roughly 2 orders of magnitude higher than that of a freshly deposited Ni film and about 3 orders of magnitude higher than that of an Fe film. The freshly deposited Ni film increases in activity by as much as 20-fold during exposure to the electrolyte (KOH); however, all films containing Fe are stable as deposited. The oxidation of Ni(OH)2 to NiOOH in Ni films occurs at potentials below the onset of the OER. Incorporation of Fe into the film increases the potential at which Ni(OH)2/NiOOH redox occurs and decreases the average oxidation state of Ni in NiOOH. The Tafel slope (40 mV dec(-1)) and reaction order in OH(-) (1) for the mixed Ni-Fe films (containing up to 95% Fe) are the same as those for aged Ni films. In situ Raman spectra acquired in 0.1 M KOH at OER potentials show two bands characteristic of NiOOH. The relative intensities of these bands vary with Fe content, indicating a change in the local environment of Ni-O. Similar changes in the relative intensities of the bands and an increase in OER activity are observed when pure Ni films are aged. These observations suggest that the OER is catalyzed by Ni in Ni-Fe films and that the presence of Fe alters the redox properties of Ni, causing a positive shift in the potential at which Ni(OH)2/NiOOH redox occurs, a decrease in the average oxidation state of the Ni sites, and a concurrent increase in the activity of Ni cations for the OER.