Large-scale industrial application of electrolytic splitting of water has called for the development of oxygen evolution electrodes that are inexpensive, robust and can deliver large current density ...(>500 mA cm(-2)) at low applied potentials. Here we show that an efficient oxygen electrode can be developed by electrodepositing amorphous mesoporous nickel-iron composite nanosheets directly onto macroporous nickel foam substrates. The as-prepared oxygen electrode exhibits high catalytic activity towards water oxidation in alkaline solutions, which only requires an overpotential of 200 mV to initiate the reaction, and is capable of delivering current densities of 500 and 1,000 mA cm(-2) at overpotentials of 240 and 270 mV, respectively. The electrode also shows prolonged stability against bulk water electrolysis at large current. Collectively, the as-prepared three-dimensional structured electrode is the most efficient oxygen evolution electrode in alkaline electrolytes reported to the best of our knowledge, and can potentially be applied for industrial scale water electrolysis.
Abstract
Hydrogen peroxide produced by electrochemical oxygen reduction reaction provides a potentially cost effective and energy efficient alternative to the industrial anthraquinone process. In ...this study, we demonstrate that by modulating the oxygen functional groups near the atomically dispersed cobalt sites with proper electrochemical/chemical treatments, a highly active and selective oxygen reduction process for hydrogen peroxide production can be obtained in acidic electrolyte, showing a negligible amount of onset overpotential and nearly 100% selectivity within a wide range of applied potentials. Combined spectroscopic results reveal that the exceptionally enhanced performance of hydrogen peroxide generation originates from the presence of epoxy groups near the Co–N
4
centers, which has resulted in the modification of the electronic structure of the cobalt atoms. Computational modeling demonstrates these electronically modified cobalt atoms will enhance the hydrogen peroxide productivity during oxygen reduction reaction in acid, providing insights into the design of electroactive materials for effective peroxide production.
Platinum is the most efficient catalyst for hydrogen evolution reaction in acidic conditions, but its widespread use has been impeded by scarcity and high cost. Herein, Pt atomic clusters (Pt ACs) ...containing Pt-O-Pt units were prepared using Co/N co-doped carbon (CoNC) as support. Pt ACs are anchored to single Co atoms on CoNC by forming strong interactions. Pt-ACs/CoNC exhibits only 24 mV overpotential at 10 mA cm
and a high mass activity of 28.6 A mg
at 50 mV, which is more than 6 times higher than commercial Pt/C with any Pt loadings. Spectroscopic measurements and computational modeling reveal the enhanced hydrogen generation activity attributes to the charge redistribution between Pt and O atoms in Pt-O-Pt units, making Pt atoms the main active sites and O linkers the assistants, thus optimizing the proton adsorption and hydrogen desorption. This work opens an avenue to fabricate noble-metal-based ACs stabilized by single-atom catalysts with desired properties for electrocatalysis.
The last decade has witnessed an extensive uptake of clean and sustainable energy sources to meet the surging energy demand while mitigating the increasing levels of greenhouse gas emission and air ...pollution. Among various energy systems, electrochemical energy storage devices such as batteries and supercapacitors have attracted worldwide attention for use in electric-powered transport, portable electronics, and biomedical devices. Recently, new multifunctional supercapacitors, which combine energy storage capability with load-carrying and other functions, offer a new "two-birds-one-stone" strategy for next-generation energy storage systems to store energy beyond the traditional systems. Multifunctional supercapacitors show great promise in reducing the size and volume of devices, improving the charge storage capacity, and minimising the cost in materials and fabrication while bringing the benefits of additional functions to the systems. This review describes the recent advances in multifunctional supercapacitors in terms of materials design, device configuration, system integration, and applications. The unique features of multifunctional supercapacitors depend strongly on architectural designs and system integration, which allow elimination of certain components to reduce the size and weight, thus improving the overall system performance. The review focuses specifically on multifunctional supercapacitors with novel mechanical, surface/interfacial, thermal, electronic, photodetection and energy harvesting/conversion functions. In addition, challenges and opportunities for further developments in the emerging field of multifunctional supercapacitors are suggested and discussed.
A comprehensive overview on the recent progress of multifunctional supercapacitors which combine energy storage capability with other functions.
Large-scale storage of renewable energy in the form of hydrogen (H2) fuel via electrolytic water splitting requires the development of water oxidation catalysts that are efficient and abundant. ...Carbon-based nanomaterials such as carbon nanotubes have attracted significant applications for use as substrates for anchoring metal-based nanoparticles. We show that, upon mild surface oxidation, hydrothermal annealing and electrochemical activation, multiwall carbon nanotubes (MWCNTs) themselves are effective water oxidation catalysts, which can initiate the oxygen evolution reaction (OER) at overpotentials of 0.3 V in alkaline media. Oxygen-containing functional groups such as ketonic CO generated on the outer wall of MWCNTs are found to play crucial roles in catalyzing OER by altering the electronic structures of the adjacent carbon atoms and facilitates the adsorption of OER intermediates. The well-preserved microscopic structures and highly conductive inner walls of MWCNTs enable efficient transport of the electrons generated during OER.
Few-layer nitrogen-doped graphene has been prepared via fast and controlled electrochemical exfoliation of graphite in a protic ionic liquid ethylammonium nitrate. The method presents a potentially ...scalable approach for preparation of metal-free, N-doped graphene for use as electrocatalysts for oxygen reduction reactions.
A considerable amount of platinum (Pt) is required to ensure an adequate rate for the oxygen reduction reaction (ORR) in fuel cells and metal‐air batteries. Thus, the implementation of atomic Pt ...catalysts holds promise for minimizing the Pt content. In this contribution, atomic Pt sites with nitrogen (N) and phosphorus (P) co‐coordination on a carbon matrix (PtNPC) are conceptually predicted and experimentally developed to alter the d‐band center of Pt, thereby promoting the intrinsic ORR activity. PtNPC with a record‐low Pt content (≈0.026 wt %) consequently shows a benchmark‐comparable activity for ORR with an onset of 1.0 VRHE and half‐wave potential of 0.85 VRHE. It also features a high stability in 15 000‐cycle tests and a superior turnover frequency of 6.80 s−1 at 0.9 VRHE. Damjanovic kinetics analysis reveals a tuned ORR kinetics of PtNPC from a mixed 2/4‐electron to a predominately 4‐electron route. It is discovered that coordinated P species significantly shifts d‐band center of Pt atoms, accounting for the exceptional performance of PtNPC.
Phosphorus‐coordinated atomic Pt‐Nx sites are theoretically predicted and experimentally realized, offering enhanced kinetics for four‐electron electrochemical oxygen reduction. Exceptional activity is attributed to the tuning of the d‐band electron center via local coordination asymmetry. This chemistry provides an effective guideline for atomic Pt catalysts in batteries and fuel cells.
Ten room temperature protic ionic liquids (RTPILs) have been prepared from low-molecular-weight Brønsted acids and amines with high purity and minimal water content, and their electrochemical ...characteristics determined using cyclic, microelectrode, and rotating disk electrode voltammetries. Potential windows of the 10 RTPILs were established at glassy carbon, gold, and platinum electrodes, where the largest potential window is generally observed with glassy carbon electrodes. The two IUPAC recommended internal potential reference systems, ferrocene/ferrocenium and cobaltocenium/cobaltocene, were determined for the 10 RTPILs, and their merits as well as limitations are discussed. Other electrochemical properties such as mass transport and double layer capacitances were also investigated. The potential applications of these RTPILs as electrolytes for electrochemical energy devices were discussed, and two novel applications using PILs for metal deposition and water electrolysis were demonstrated.
Gold nanoparticles incorporated in mesoporous cobalt oxides (Au/mCo3O4) are fabricated by a nanocasting method using porous silica as the hard template. The Au/mCo3O4 material exhibits enhanced ...catalytic activity towards water oxidation compared to bulk mCo3O4 in both alkaline and neutral solutions. The superior catalytic performance is ascribed to the synergistic effect of electronegative metal gold, which facilitates the generation of active CoIV sites, as well as the large specific surface area and the preferential exposure of catalytic active crystalline lattice.
Gold rush: A material comprising electronegative gold nanoparticles incorporated into mesoporous cobalt oxide (Au/mCo3O4) is capable of catalyzing the oxygen evolution reaction at low overpotentials and high current densities in alkaline and neutral media. The high catalytic activity is attributed to its large reactive surface area, synergistic effects between Au and Co3O4, as well as preferential exposure of catalytically active crystalline lattices.
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