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![Layered structure of transition-metal chalcogenides with acomposition of MX 2 .Reproduced with permission from reference [14].Copyright 2015, American Chemical Society.](profile/Ailong-Li/publication/327552904/figure/fig1/AS:11431281085004470@1663560054822/Layered-structure-of-transition-metal-chalcogenides-with-acomposition-of-MX-2-Reproduced.png)
Layered structure of transition-metal chalcogenides with acomposition of MX 2 .Reproduced with permission from reference [14].Copyright 2015, American Chemical Society.
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Fundamentals of water electrolysis, and recent research progresses and trends in the development of earth‐abundant first row transition metal (Mn, Fe, Co, Ni, Cu) based oxygen evolution reaction (OER) and hydrogen evolution (HER) electrocatalysts working in acidic, alkaline or neutral conditions are reviewed. The HER catalysts include mainly metal...
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Context 1
... appearance of metal chalcogenides has had ap rofound impact on the development of noble-metal-free hydrogen evolution catalysts. One representative type is layered transitionmetal chalcogenides with the compositiono fM X 2 (M = Mo or Wa nd X = So rS e) exhibiting 1T (tetragonal, AA stacking), 2H (hexagonal, ABAB stacking) or 3R (rhombohedral, ABCABC stacking) polymorphs ( Figure 3). The first two phases are commonly seen in chalcogenide catalysts for water electrolysis.The 1T polymorph is am etallic X-M-X single layer,w hich consists of edge-sharing MX 6 octahedra. ...
Context 2
... hydrogen adsorption on the metal carbides urfacesa re sensitively decreased along with increasing surface coverage (Figure12b,c), leading to increased HER activities. [67] 2D ( Figure 13a). Increasing the Mo/C atom ratio may introduce some carbon vacancies, which will decrease the accumulation of H-adatomsa nd alleviate hydrogen evolution. ...
Context 3
... neighboringCatoms act as both electron acceptors and donors, suggesting ac omplex electrontransfer process of Mo 2 C!C!Ni nM o 2 C@NC catalyst. The C atomsa djacent to Na toms in the carbonl ayer were identified to be the catalytically active sites responsible for the high activity of the Mo 2 C@NC (Figure 13b). [69] Figure 12. a) Volcano plots for the HER on various transition metals and metal carbides. ...
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Electrochemical water splitting is a promising technology for sustainable conversion, storage, and transport of hydrogen energy. Searching for earth‐abundant hydrogen/oxygen evolution reaction (HER/OER) electrocatalysts with high activity and durability to replace noble‐metal‐based catalysts plays paramount importance in the scalable application of...
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Water splitting to produce hydrogen gas, using renewably produced electricity (electrocatalysis) or by direct conversion of solar energy (photocatalysis), is a strategy that addresses key environmental and energy challenges. The overall water splitting reaction proceeds as two half reactions, namely the oxygen evolution reaction (OER) and hydrogen...
Transition metal phosphides have high catalytic performance and stability among non-precious metal electrocatalysts, particularly exhibiting good hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance in alkaline solutions, due to the platinum-like electronic structure of transition metal phosphides. In this study, we suc...
Citations
... R s values can be estimated by fitting an equivalent circuit model to the impedance data ( Fig. 6(b)), indicating that the high P content improves the activity of the catalysts, and Ni 70.2 Mo 27.0 P 2.8 /CF catalyst exhibits the best catalytic activity. Doping P increases the electron density of Ni-Mo and decreases the d-band center, which is related to the nature of adsorption in the catalytic HER process, the downshifting of the -d-band weakens the adsorption of H * on the electrocatalysts, reducing the strong binding energy of Ni to H * (ΔG H* < 0), bringing it closer to the desired value, accelerating the desorption process and increasing the catalytic activity of the catalysts [74]. ...
Decarbonization of transportation sector is critical to achieve net-zero emissions economy by 2060. It is of importance to develop highly efficient electrocatalysts for decarbonization. Ni-Mo-P ternary alloy catalysts were electrodeposited on Cu foam (CF), and the rough surface of Ni-Mo-P/CF catalysts was composed of uniformly dense small clusters with the size of 200 nm. The catalyst was composed of a mixture of nanocrystals and amorphous, with metallic Ni and its solid solution, Ni and Mo oxides, and Ni(OH)2. The Ni70.2Mo27.0P2.8/CF catalyst exhibited Tafel slope of 63.1 mV·dec⁻¹ in alkaline medium, and delivered a current density of 10 mA·cm⁻² at an overpotential of 68 mV, demonstrating the excellent hydrogen evolution reaction (HER) activity due to the large active surface area, the synergistic effect and high electrical conductivity of the electrode. After 1000 cycles testing, Ni70.2Mo27.0P2.8/CF catalyst showed an increase of 2.8 mV in hydrogen evolution overpotential and almost no voltage decay was present in chronopotentiometric test for 10 h. The good HER performance of Ni-Mo-P/CF catalysts had a significant potential to be utilized in commercial water electrolyzer.
Graphical Abstract
... During cathodic catalysis, large amounts of OHstimulate the production of nickel hydroxide [51]. According to the Pourbaix diagram for Ni/H2O [20], for water reduction potential in a strong alkaline environment, a Ni cathode would be the Ni or Ni hydroxide [20,52]. With fluctuating power, the cathode state cannot be sustained in the water reduction potential, and a higher potential would lead to the oxidation of Ni and Ni hydroxide to form NiOOH or Ni oxides. ...
The combination of water electrolysis and renewable energy to produce hydrogen is a promising way to solve the climate and energy crisis. However, the fluctuating characteristics of renewable energy not only present a significant challenge to the use of water electrolysis electrodes, but also limit the development of the hydrogen production industry. In this study, the effects of three different types of waveforms (square, step, and triangle, which were used to simulate the power input of renewable energy) on the electrochemical catalysis behavior of Ni plate cathodes for HER was investigated. During the test, the HER performance of the Ni cathode increased at first and then slightly decreased. The fluctuating power led to the degradation of the Ni cathode surface, which enhanced the catalysis effect by increasing the catalytic area and the active sites. However, prolonged operation under power fluctuations could have damaged the morphology of the electrode surface and the substances comprising this surface, potentially resulting in a decline in catalytic efficiency. In addition, the electrochemical catalysis behavior of the prepared FeNiMo-LDH@NiMo/SS cathode when subjected to square-wave potential with different fluctuation amplitudes was also extensively studied. A larger amplitude of fluctuating power led to a change in the overpotential and stability of the LDH electrode, which accelerated the degradation of the cathode. This research provides a technological basis for the coupling of water electrolysis and fluctuating renewable energy and thus offers assistance to the development of the “green hydrogen” industry.
... The OER performance is related to the intrinsic activity of a catalyst, depending on the electrochemically active sites [4]. Several materials have been proposed for OER, such as layered doublehydroxides (LDH), metal-organic frameworks (MOFs) or chalcogenides and perovskites [7][8][9][10][11]. These metal-based catalysts have limitations such as the need for critical raw materials and their high processing costs [12]. ...
Nowadays, energy conversion and storage technologies are essential research topics due to the necessity of more sustainable processes. Specifically, water splitting is highly affected by slow kinetics and limited knowledge of the oxygen evolution reaction (OER). This work envisages the preparation of graphitic carbon nitride (g-C3N4) electrocatalysts for efficient OER by a facile one-pot method. The impact of the preparation temperature (450–650 °C) of g-C3N4 was assessed for the first time on water splitting processes and explained by different characterisation techniques. The unique crystal structure, surface chemistry, and electronic properties of the material prepared at 550 °C lead to a remarkable OER efficiency, with an overpotential of 355 mV at 10 mA cm−2 and a Tafel slope of 46.8 mV dec−1. Interestingly, three major differences were observed when comparing the material prepared at 550 °C with those obtained at other temperatures: the reduced structural distortion, the superior composition in oxygen and the presence of terminal functional groups. Also, compared to other metal-free g-C3N4 electrocatalysts reported in the literature, we achieved lower Tafel slope values without additional post-treatments or co-catalysts. Hence, for the first time a metal-free catalyst defeats benchmark IrO2. The prepared electrodes were stable for up to 45 h, even when increasing the applied current density to 100 mA cm−2 for 15 h. Thus, this work provides a simple route for the fabrication of highly-efficient and long-lasting electrocatalysts for a remarkable OER performance.
... The need for sustainable energy solutions has stimulated the development of techniques for reusing scarce resources and achieving high-energy storage capabilities [1,2]. The efficient utilization of earth-abundant transition-metal-based materials can fulfill these requirements, due to their cost-effectiveness and high activity [3][4][5][6]. Recently, lithium-ion batteries (LIBs) have been developed for a wide range of electronic applications due to their high specific capacitance, low cost, and reversible redox properties [7][8][9][10]. ...
The polyol process is a straightforward method to produce metallic compounds through transformation from metal salt. An optimized procedure based on the polyol process in this research was developed for the selective synthesis of α-nickel hydroxide from metal salt. From various experimental results, the preparation of the sodium salt of ethylene glycol was crucial for the efficient production of α-nickel hydroxide. The structure of α-nickel hydroxide was studied by powder X-ray diffraction, IR spectroscopy, thermogravimetric analysis, transmission electron microscopy, and scanning electron microscope. The estimated Gibbs free energies for each step of the polyol process, employing density functional theory (DFT) calculations, confirmed the formation of nickel reaction intermediates, which mitigated the production of metallic nickel. The innovative point of this research is the finding that the intentional generation of nickel reaction intermediates leads to selective synthesis of α-nickel hydroxide.
... which is a key parameter for characterizing HER activity, the downshifting of the -d-band weakens the H * adsorption strength, reducing the strong binding energy of Ni, Co to H * (ΔG H* < 0) [53,54]. As the bonding of H 2 was weaker on Ni-Ir, Co-Ir alloy surface, the produced H 2 became easier to desorb from the catalysts. ...
M-iridium (M = cobalt (Co), nickel (Ni)) bimetallic alloy catalysts with low iridium (Ir) loading of 0.3–2.0 mg·cm⁻² were prepared on copper foam (CF) supports by electrodeposition. The top surface of as-deposited M-Ir catalysts was mainly composed of metallic state and oxides states, such as metallic Ir, Ni(OH)2 or Co(OH)2, Co(Ir) and Ni(Ir) solid solution, Ir oxides. M-Ir catalysts with low Ir loading exhibited excellent catalytic performance. Ni63.4Ir36.6/CF catalyst with low Ir loading of 1.8 mg·cm⁻² achieved a current density of 10 mA·cm² at an overpotential of 52 mV and a Tafel slope of 36 mV·dec⁻¹. Co64.2Ir35.8/CF catalyst with low Ir loading of 0.7 mg·cm⁻² was uniformly scattered with small ellipsoidal particles, looking like fine fluff, requiring an overpotential of 51 mV for hydrogen evolution reaction to reach a current density of 10 mA·cm⁻², having a Tafel slope of 38 mV·dec⁻¹. After long-term hydrogen evolution testing, M-Ir/CF catalysts exhibited excellent electrocatalytic stability for water splitting in alkaline solution.
Graphical Abstract
... The Mn and Fe site metal cations dissolved during the OER and can be freed from the bulk electrolyte due to material deprivation or recombination with the OH − of electrolyte and then re-adherence on the surface of catalyst to form an oxyhydroxide phase. From previous literature on ABO 3 (MnFeO 3 ) perovskite structure, a strong interface exists in the electrode/electrolyte during OER which permits building the stable symmetry between Fe insertion and degradation/dissolution speed in the Mn x O y endorsed by Fe (aq) in the electrolyte and major role in the OER process [57,58]. Based on the literature [59], the Tafel slope of 41 mV dec − 1 indicates the establishment of MO (where M stands for the active edge on the catalyst surface) through the adsorbed OH − ions by the speed deciding stage. ...
... The Mn and Fe site metal cations dissolved during the OER and can be freed from the bulk electrolyte due to material deprivation or recombination with the OH − of electrolyte and then re-adherence on the surface of catalyst to form an oxyhydroxide phase. From previous literature on ABO 3 (MnFeO 3 ) perovskite structure, a strong interface exists in the electrode/electrolyte during OER which permits building the stable symmetry between Fe insertion and degradation/dissolution speed in the Mn x O y endorsed by Fe (aq) in the electrolyte and major role in the OER process [57,58]. Based on the literature [59], the Tafel slope of 41 mV dec − 1 indicates the establishment of MO (where M stands for the active edge on the catalyst surface) through the adsorbed OH − ions by the speed deciding stage. ...
... Reducing the power consumption of PTH is one of the key ways to further improve the energy efficiency of the GH-CTM process; therefore, it is essential to develop a new type of PTH catalyst. For example, Yao et al. had obtained outstanding improvement in water electrolysis yield by the use of catalysts [52,53]. ...
Given the importance of energy and its role in sustainable gas production, paying special attention to its consumption indicators in all industries, especially oil & gas is very important. The energy consumption index parameter, which equals the ratio of energy consumption to gas production, is one of the most significant indicators of the gas refinery. Artificial intelligence can be used to evaluate the effects of different parameters and find the factors influencing energy performance. Important variables such as inlet gas from various sources, the energy consumption of each part, and the amount of waste refinery gas are collected on different days of the year, then using the least square support vector machine method and networking and sensitivity analysis of the impact of each variable separately. The role of each in this parameter is determined so that it can be used to provide appropriate solutions to reduce energy consumption and the energy consumption index parameter for sustainable gas production. According to the results of this study, the steam unit has a 14 % impact on the energy consumption index, and the gas sweetening unit has an 18 % impact on gas consumption. So, more research on the optimization of these two units is necessary.
... The characteristic peak of Ir shifts in the direction of low binding energy, leading to the downshifting of the -d-band [49]. The -d band center is directly related to the nature of adsorption in the catalytic process, the downshifting of the -d-band weakens the H adsorption strength, reducing the strong binding energy of Ni to H * (ΔG H* <0), accelerating the desorption process of the catalyst and increasing the catalytic activity [50,51]. ...
M-iridium (M = cobalt (Co), nickel (Ni)) bimetallic alloy catalysts with low iridium (Ir) loading of 0.3 ~ 2.0 mg·cm − 2 were prepared on copper foam (CF) supports by electrodeposition. The top surface of as-deposited M-Ir catalysts was mainly composed of metallic state and oxides states, such as metallic Ir, Ni(OH) 2 or Co(OH) 2 , Co(Ir) and Ni(Ir) solid solution, Ir oxides. M-Ir catalysts with low Ir loading exhibited excellent catalytic performance. Ni 67.4 Ir 32.6 /CF catalyst with low Ir loading of 2.0 mg·cm − 2 achieved a current density of 10 mA·cm ² at an overpotential of 52 mV and a Tafel slope of 36 mV·dec − 1 . Co 64.2 Ir 35.8 /CF catalyst with low Ir loading of 0.7 mg·cm − 2 was uniformly scattered with small ellipsoidal particles, looking like fine fluff, requiring an overpotential of 51 mV for hydrogen evolution reaction to reach a current density of 10 mA·cm − 2 , having a Tafel slope of 38 mV·dec − 1 . After long-term hydrogen evolution testing, M-Ir/CF catalysts exhibited excellent electrocatalytic stability for water splitting in alkaline solution.
... Currently, noble metal-based catalysts are widely used in the actual hydrogen production from water splitting, but precious metals are rare and have poor stability, hindering their large-scale practical application [6,7]. Compounds utilizing transition metals such as Ni, Co, Fe, Mn, and Mo have been commonly used by many research groups due to their low cost, simple preparation process, and wide range of sources [8][9][10]. In recent years, during the process of finding new high-performance bifunctional catalysts and well-integrated catalytic electrodes for OWS to replace precious metals, different transition metal-based materials have been reported, including sulfides, carbides, and phosphides [11][12][13][14][15][16]. ...
