Direct One-Step Growth of Bimetallic Ni2Mo3N on Ni Foam as an Efficient Oxygen Evolution Electrocatalyst.
TL;DR: In this paper, a simple and economical synthetic route for direct one-step growth of bimetallic Ni2Mo3N nanoparticles on Ni foam substrate and its catalytic performance during an oxygen evolution reaction (OER) was reported.
Abstract: A simple and economical synthetic route for direct one-step growth of bimetallic Ni2Mo3N nanoparticles on Ni foam substrate (Ni2Mo3N/NF) and its catalytic performance during an oxygen evolution reaction (OER) are reported. The Ni2Mo3N/NF catalyst was obtained by annealing a mixture of a Mo precursor, Ni foam, and urea at 600 °C under N2 flow using one-pot synthesis. Moreover, the Ni2Mo3N/NF exhibited high OER activity with low overpotential values (336.38 mV at 50 mA cm−2 and 392.49 mV at 100 mA cm−2) and good stability for 5 h in Fe-purified alkaline electrolyte. The Ni2Mo3N nanoparticle surfaces converted into amorphous surface oxide species during the OER, which might be attributed to the OER activity.
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TL;DR: In this paper , the surface geometric and electronic structure and activity of nonmetal atoms (X, X = B, C, N, O, P)-doped Ni3S2 (X-Ni3S 2) were studied to screen high-performance Ni 3S2-based OER electrocatalysts through density functional theory calculation.
Abstract: Heteroatom doping is an effective strategy to regulate electrocatalysts for the oxygen evolution reaction (OER). Nonmetal heteroatoms can effectively engineer geometric and electronic structures and activating surface sites of catalysts due to their unique radius and the electronegativity of nonmetal atoms. Hence, the surface geometric and electronic structure and activity of nonmetal atoms (X, X = B, C, N, O, P)-doped Ni3S2 (X-Ni3S2) were studied to screen high-performance Ni3S2-based OER electrocatalysts through density functional theory calculation. Theoretical results demonstrated that dopants in X-Ni3S2 can alter bond length and charge of surface, modify active sites for intermediates adsorption, and adjust the theoretical overpotential. Among all dopants, C can effectively modulate surface structure, activate surface sites, weaken the adsorption of key intermediates, decrease theoretical overpotential, and enable C-Ni3S2 with the best theoretical OER activity among all X-Ni3S2 with the lowest theoretical overpotential (0.46 eV). Further experimental results verified that the synthesized C-Ni3S2 performed an improved OER activity in the alkaline condition with a considerably enhanced overpotential of 261 mV at 10 mA cm−2 as well as a Tafel slope of 95 mV dec−1 compared to pristine Ni3S2.
7 citations
TL;DR: In this article , the NiMoO4 precursor was firstly synthesized by facile hydrothermal reaction, and then the self-supported NiMo alloy was synthesised by annealing.
Abstract: Hydrogen attracts researchers′ attention because its combustion products are very clean and will not pollute the environment. Electrocatalytic water splitting is a sustainable hydrogen energy production technology, which splits water into hydrogen and oxygen. In electrocatalytic water splitting, high activity catalysts can reduce the potential barrier of catalytic reaction and speed up the reaction, among which transition metal alloy catalysts have attracted extensive attention in the application of electrocatalysis due to their excellent electrochemical activity, stability and easy preparation. In this paper, the NiMoO4 precursor was firstly synthesized by the facile hydrothermal reaction, and then the self-supported NiMo alloy was synthesized by annealing. The results indicate that NiMo alloy has efficient hydrogen evolution activity (34 mV) and oxygen evolution activity (279 mV) at 10 mA cm−2. More importantly, the water splitting system consisting of NiMo alloys demonstrates excellent performance and stability. At 10 mA cm−2, the voltage is 1.489 V, and it can be stable for at least 10 hours at 70 mA cm−2. This study can provide some ideas for the study of water splitting electrocatalysts.
3 citations
TL;DR: In this paper , a two-step method including hydrothermal and nitridation reactions to in situ synthesize NiMoN nanorod arrays with abundant active sites and a fast electron transfer rate on nickel foam substrate was proposed.
Abstract: The development of cheap and highly active electrocatalysts for efficient water splitting is crucial for the production of green hydrogen at a low cost. In this work, we proposed a two-step method including hydrothermal and nitridation reactions to in situ synthesize NiMoN nanorod arrays with abundant active sites and a fast electron transfer rate on nickel foam substrate. The optimal tailoring of the Ni/Mo ratio leads to a high concentration of active Mo3+ species and suitable Ni doping content in the NiMoN catalyst, which shows superior hydrogen evolution reaction performance. The overpotentials at the current densities of 10 and 100 mA/cm2 are only 20 and 46 mV, which are better than those of the most reported NiMoN-based catalysts and even the commercial benchmark material of Pt/C. Additionally, the electrocatalyst also shows excellent long-term stability after 24 h tests at densities of 10 and 100 mA/cm2, possessing great potential for industrial applications for water splitting to produce hydrogen.
3 citations
TL;DR: In this paper , the authors report that free-standing Co2Mo3N and Ni2Mo 3N achieve overpotentials of 149 ± 8 and 158 ± 10 mV (in 0.5 M H2SO4) at a benchmark current density of 10 mA cm-2.
Abstract: Proton exchange membrane electrolyzers are considered the most advanced devices for producing green hydrogen by water electrolysis. Their development requires catalytic materials that are stable under acidic conditions and drive the hydrogen evolution reaction (HER) forward efficiently which makes research into the identification of the catalytic sites important. We report that free-standing Co2Mo3N and Ni2Mo3N achieve overpotentials of 149 ± 8 and 158 ± 10 mV (in 0.5 M H2SO4) at a benchmark current density of 10 mA cm–2. Both nitrides remained stable and consistently deliver current densities >500 mA cm–2 at a potential as low as 308 ± 22 mV when they were immobilized on nickel foam. Replacing Ni for Fe in Ni2Mo3N leads to FexNi2–xMo3N (0.5 ≤ x ≤ 1.25) that show a decrease in catalytic activity as the value of x increases which confirms that Ni (rather than Mo and N) sites are catalytically active. The X-ray photoelectron spectroscopy data additionally suggests that preserving the low oxidation states of transition metals in the nitrides is important for achieving good catalytic performance toward the HER in acidic electrolytes.
1 citations
TL;DR: In this article , the main focus is given to the most significant innovations in the surface topography, morphological shape, size distribution, and electrocatalytic functionality of highly engineered molybdenum nitride catalysts.
Abstract: The advancement of spotless hydrogen energy generation is being accelerated by the advancement in nonprecious electrocatalysts for effective hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water splitting. In this review, the main focus is given to the most significant innovations in the surface topography, morphological shape, size distribution, and electrocatalytic functionality of highly engineered molybdenum nitride catalysts, equal to or even better than state-of-the-art electrocatalyst for HER and OER. Different morphological or interfacial engineering techniques, such as in situ electrospinning, topochemical methods, and classic chemical methods for synthesizing nonprecious molybdenum nitride electrocatalysts, are extensively covered. Molybdenum nitrides are discovered the excellent electrocatalyst, and the factors that can improve its electrocatalytic properties, such as morphological tuning, controlled geometrical composition, pH effect, hybrid and electronic structures, the effect of temperature, and effects of active sites, are comprehensively discussed.
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TL;DR: Identifying and building a sustainable energy system are perhaps two of the most critical issues that today's society must address.
Abstract: Identifying and building a sustainable energy system are perhaps two of the most critical issues that today's society must address. Replacing our current energy carrier mix with a sustainable fuel is one of the key pieces in that system. Hydrogen as an energy carrier, primarily derived from water, can address issues of sustainability, environmental emissions, and energy security. Issues relating to hydrogen production pathways are addressed here. Future energy systems require money and energy to build. Given that the United States has a finite supply of both, hard decisions must be made about the path forward, and this path must be followed with a sustained and focused effort.
4,824 citations
TL;DR: Measurements of activity as a function of film thickness on Au and glassy carbon substrates are consistent with the hypothesis that Fe exerts a partial-charge-transfer activation effect on Ni, similar to that observed for noble-metal electrode surfaces.
Abstract: Fe plays a critical, but not yet understood, role in enhancing the activity of the Ni-based oxygen evolution reaction (OER) electrocatalysts. We report electrochemical, in situ electrical, photoelectron spectroscopy, and X-ray diffraction measurements on Ni1–xFex(OH)2/Ni1–xFexOOH thin films to investigate the changes in electronic properties, OER activity, and structure as a result of Fe inclusion. We developed a simple method for purification of KOH electrolyte that uses precipitated bulk Ni(OH)2 to absorb Fe impurities. Cyclic voltammetry on rigorously Fe-free Ni(OH)2/NiOOH reveals new Ni redox features and no significant OER current until >400 mV overpotential, different from previous reports which were likely affected by Fe impurities. We show through controlled crystallization that β-NiOOH is less active for OER than the disordered γ-NiOOH starting material and that previous reports of increased activity for β-NiOOH are due to incorporation of Fe-impurities during the crystallization process. Through...
2,419 citations
11 Jan 2017
TL;DR: In this article, the authors investigate progress towards photo-electrocatalytic water-splitting systems, with special emphasis on how they might be incorporated into photoelectrocaralyst systems.
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.
2,369 citations
TL;DR: The synthesis of ultrathin nickel-iron layered double hydroxide nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs) induced the formation of NiFe-LDH, which exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.
Abstract: Highly active, durable, and cost-effective electrocatalysts for water oxidation to evolve oxygen gas hold a key to a range of renewable energy solutions, including water-splitting and rechargeable metal–air batteries. Here, we report the synthesis of ultrathin nickel–iron layered double hydroxide (NiFe-LDH) nanoplates on mildly oxidized multiwalled carbon nanotubes (CNTs). Incorporation of Fe into the nickel hydroxide induced the formation of NiFe-LDH. The crystalline NiFe-LDH phase in nanoplate form is found to be highly active for oxygen evolution reaction in alkaline solutions. For NiFe-LDH grown on a network of CNTs, the resulting NiFe-LDH/CNT complex exhibits higher electrocatalytic activity and stability for oxygen evolution than commercial precious metal Ir catalysts.
2,320 citations
IBM1
TL;DR: In this article, the authors summarized the promise and challenges facing development of practical Li−air batteries and the current understanding of its chemistry, and showed that the fundamental battery chemistry during discharge is the electrochemical oxidation of lithium metal at the anode and reduction of oxygen from air at the cathode.
Abstract: The lithium−air system captured worldwide attention in 2009 as a possible battery for electric vehicle propulsion applications. If successfully developed, this battery could provide an energy source for electric vehicles rivaling that of gasoline in terms of usable energy density. However, there are numerous scientific and technical challenges that must be overcome if this alluring promise is to turn into reality. The fundamental battery chemistry during discharge is thought to be the electrochemical oxidation of lithium metal at the anode and reduction of oxygen from air at the cathode. With aprotic electrolytes, as used in Li-ion batteries, there is some evidence that the process can be reversed by applying an external potential, i.e., that such a battery can be electrically recharged. This paper summarizes the authors’ view of the promise and challenges facing development of practical Li−air batteries and the current understanding of its chemistry. However, it must be appreciated that this perspective ...
2,308 citations