Ag@CoxP Core–Shell Heterogeneous Nanoparticles as Efficient Oxygen Evolution Reaction Catalysts
TL;DR: In this paper, a facile synthetic method that yields Ag@CoxP core-shell-type heterogeneous nanostructures with excellent oxygen evolution reaction (OER) activity was presented.
Abstract: We present a facile synthetic method that yields Ag@CoxP core–shell-type heterogeneous nanostructures with excellent oxygen evolution reaction (OER) activity. This nanocatalyst can deliver a current density of 10 mA/cm2 at a small overpotential of 310 mV and exhibits high catalytic stability. Additionally, the catalytic activity of Ag@CoxP is 8 times higher than that of the Co2P nanoparticles, owing primarily to the strong electronic interaction between the Ag core and the CoxP shell.
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TL;DR: The experimental results demonstrate that the NiCo@NiCoO2 /C PMRAs as electrocatalysts exhibit high catalytic activity, low overpotential, and high stability for OER in alkaline media.
Abstract: The study of cost-efficient and high-performance electrocatalysts for oxygen evolution reaction (OER) has attracted much attention. Here, porous microrod arrays constructed by carbon-confined NiCo@NiCoO2 core@shell nanoparticles (NiCo@NiCoO2 /C PMRAs) are fabricated by the reductive carbonization of bimetallic (Ni, Co) metal-organic framework microrod arrays (denoted as NiCo-MOF MRAs) and subsequent controlled oxidative calcination. They successfully combine the desired merits including large specific surface areas, high conductivity, and multiple electrocatalytic active sites for OER. In addition, the oxygen vacancies in NiCo@NiCoO2 /C PMRAs significantly improve the conductivity of NiCoO2 and accelerate the kinetics of OER. The above advantages obviously enhance the electrocatalytic performance of NiCo@NiCoO2 /C PMRAs. The experimental results demonstrate that the NiCo@NiCoO2 /C PMRAs as electrocatalysts exhibit high catalytic activity, low overpotential, and high stability for OER in alkaline media. The strategy reported will open up a new route for the fabrication of porous bimetallic composite electrocatalysts derived from MOFs with controllable morphology for electrochemical energy conversion devices.
355 citations
TL;DR: Carbon-based materials are widely employed as metal-free catalysts or supports in catalysis, energy, and ecological applications because of their interesting properties as mentioned in this paper, and their high surfa...
Abstract: Carbon-based materials are widely employed as metal-free catalysts or supports in catalysis, energy, and ecological applications because of their interesting properties. Generally, their high surfa...
335 citations
TL;DR: In this article, a facile method to synthesize self-assembled 3D laminar NiCo2Px anchored on functionalized carbon nanotubes was developed for achieving cost-efficient, highly-active, and robust electrocatalysts towards overall water splitting in 1 M KOH.
Abstract: Hydrogen is a promising energy carrier that becomes an alternative to fossil fuels due to its recyclability and pollution-free nature. Water splitting is an effective method for high purity hydrogen production; however, it requires efficient, low-cost and durable catalysts. Herein, a facile method to synthesize self-assembled 3D laminar NiCo2Px anchored on functionalized carbon nanotubes (NiCo2Px/CNTs) is developed for achieving cost-efficient, highly-active, and robust electrocatalysts towards overall water splitting in 1 M KOH. Notably, the overpotentials at a current density of 10 mA cm−2 are as low as 47 and 284 mV for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively. The water electrolyzer device using NiCo2Px/CNTs as both the cathode and anode only requires a cell voltage of 1.61 V to reach a current density of 10 mA cm−2 along with outstanding durability for at least 48 h. Furthermore, the catalytic mechanism was discussed with a special emphasis on the synergetic effect of Ni and Co and real OER active species. Our work not only establishes a promising electrocatalyst, but also provides a general strategy to enhance the activity and stability of metal phosphides.
279 citations
TL;DR: In this article, a review summarizes selected and most recent espoused synthetic methodologies for their assembly including the formation of magnetic COFs and potential insights in the field of catalysis; electrocatalysis; and photocatalysis where COFs can serve as excellent platforms for supporting catalytic species, are also illustrated.
Abstract: Covalent organic frameworks (COFs) are one of the most important and dynamic members of the porous organic materials and are constructed using reticular chemistry with the building blocks being connected via covalent bonds. Due to their fascinating properties such as large surface area; structural versatility; effortless surface modification; and high chemical stability, COFs are being widely deployed in catalytic; sensing; adsorption; gas storage; and many other valuable applications. This review summarizes selected and most recent espoused synthetic methodologies for their assembly including the formation of magnetic COFs. Potential insights in the field of catalysis; electrocatalysis; and photocatalysis, where COFs can serve as excellent platforms for supporting catalytic species, are also illustrated.
237 citations
TL;DR: Owing to disposition on the original defects of BP, Co2 P improves the conductivity and offers more active electrocatalytic sites, so that the BP/Co2 P nanosheets exhibit better and more stable electrocatalyst activities in the hydrogen evolution and oxygen evolution reactions.
Abstract: Heterostructures composed of two-dimensional black phosphorus (2D BP) with unique physical/chemical properties are of great interest. Herein, we report a simple solvothermal method to synthesize in-plane BP/Co2 P heterostructures for electrocatalysis. By using the reactive edge defects of the BP nanosheets as the initial sites, Co2 P nanocrystals are selectively grown on the BP edges to form the in-plane BP/Co2 P heterostructures. Owing to disposition on the original defects of BP, Co2 P improves the conductivity and offers more active electrocatalytic sites, so that the BP/Co2 P nanosheets exhibit better and more stable electrocatalytic activities in the hydrogen evolution and oxygen evolution reactions. Our work not only extends the application of BP to electrochemistry, but also provides a new idea to improve the performance of BP by utilization of defects. Furthermore, this strategy can be extended to produce other BP heterostructures to expand the corresponding applications.
222 citations
References
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TL;DR: The biggest challenge is whether or not the goals need to be met to fully utilize solar energy for the global energy demand can be met in a costeffective way on the terawatt scale.
Abstract: Energy harvested directly from sunlight offers a desirable approach toward fulfilling, with minimal environmental impact, the need for clean energy. Solar energy is a decentralized and inexhaustible natural resource, with the magnitude of the available solar power striking the earth’s surface at any one instant equal to 130 million 500 MW power plants.1 However, several important goals need to be met to fully utilize solar energy for the global energy demand. First, the means for solar energy conversion, storage, and distribution should be environmentally benign, i.e. protecting ecosystems instead of steadily weakening them. The next important goal is to provide a stable, constant energy flux. Due to the daily and seasonal variability in renewable energy sources such as sunlight, energy harvested from the sun needs to be efficiently converted into chemical fuel that can be stored, transported, and used upon demand. The biggest challenge is whether or not these goals can be met in a costeffective way on the terawatt scale.2
8,037 citations
TL;DR: In this paper, the authors report a protocol for evaluating the activity, stability, and Faradaic efficiency of electrodeposited oxygen-evolving electrocatalysts for water oxidation.
Abstract: Objective evaluation of the activity of electrocatalysts for water oxidation is of fundamental importance for the development of promising energy conversion technologies including integrated solar water-splitting devices, water electrolyzers, and Li-air batteries. However, current methods employed to evaluate oxygen-evolving catalysts are not standardized, making it difficult to compare the activity and stability of these materials. We report a protocol for evaluating the activity, stability, and Faradaic efficiency of electrodeposited oxygen-evolving electrocatalysts. In particular, we focus on methods for determining electrochemically active surface area and measuring electrocatalytic activity and stability under conditions relevant to an integrated solar water-splitting device. Our primary figure of merit is the overpotential required to achieve a current density of 10 mA cm–2 per geometric area, approximately the current density expected for a 10% efficient solar-to-fuels conversion device. Utilizing ...
4,808 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: In this paper, the Ni2P nanoparticles were used as both cathode and anode catalysts for an alkaline electrolyzer, which generated 10 mA cm−2 at 1.63 V.
Abstract: Electrochemical water splitting into hydrogen and oxygen is a promising method for solar energy storage. The development of efficient electrocatalysts for water splitting has drawn much attention. However, catalysts that are active for both the hydrogen evolution and oxygen evolution reactions are rare. Herein, we show for the first time that nickel phosphide (Ni2P), an excellent hydrogen evolving catalyst, is also highly active for oxygen evolution. A current density of 10 mA cm−2 is generated at an overpotential of only 290 mV in 1 M KOH. The high activity is attributed to the core–shell (Ni2P/NiOx) structure that the material adopts under catalytic conditions. The Ni2P nanoparticles can serve as both cathode and anode catalysts for an alkaline electrolyzer, which generates 10 mA cm−2 at 1.63 V.
1,374 citations
TL;DR: Investigation of the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates revealed that the as-deposited cobALT oxide is present as Co(3)O(4) but undergoes progressive oxidation to CoO(OH) with increasing anodic potential.
Abstract: Scanning electron microscopy, linear sweep voltammetry, chronoamperometry, and in situ surface-enhanced Raman spectroscopy were used to investigate the electrochemical oxygen evolution reaction (OER) occurring on cobalt oxide films deposited on Au and other metal substrates. All experiments were carried out in 0.1 M KOH. A remarkable finding is that the turnover frequency for the OER exhibited by ∼0.4 ML of cobalt oxide deposited on Au is 40 times higher than that of bulk cobalt oxide. The activity of small amounts of cobalt oxide deposited on Pt, Pd, Cu, and Co decreased monotonically in the order Au > Pt > Pd > Cu > Co, paralleling the decreasing electronegativity of the substrate metal. Another notable finding is that the OER turnover frequency for ∼0.4 ML of cobalt oxide deposited on Au is nearly three times higher than that for bulk Ir. Raman spectroscopy revealed that the as-deposited cobalt oxide is present as Co3O4 but undergoes progressive oxidation to CoO(OH) with increasing anodic potential. Th...
1,204 citations