The electrocatalytic conversion of CO2 into value‐added chemicals is a promising approach to realize a carbon‐energy balance. However, low current density still limits the application of the CO2 ...electroreduction reaction (CO2RR). Metal–organic frameworks (MOFs) are one class of promising alternatives for the CO2RR due to their periodically arranged isolated metal active sites. However, the poor conductivity of traditional MOFs usually results in a low current density in CO2RR. We have prepared conductive two‐dimensional (2D) phthalocyanine‐based MOF (NiPc‐NiO4) nanosheets linked by nickel‐catecholate, which can be employed as highly efficient electrocatalysts for the CO2RR to CO. The obtained NiPc‐NiO4 has a good conductivity and exhibited a very high selectivity of 98.4 % toward CO production and a large CO partial current density of 34.5 mA cm−2, outperforming the reported MOF catalysts. This work highlights the potential of conductive crystalline frameworks in electrocatalysis.
Nickel phthalocyanine molecules as active sites were installed into nickel‐catecholate‐linked 2D conductive metal–organic framework nanosheets for efficient CO2 electroreduction with nearly 100 % CO selectivity.
Bismuth (Bi) is a topological crystalline insulator (TCI), which has gapless topological surface states (TSSs) protected by a specific crystalline symmetry that strongly depends on the facet. Bi is ...also a promising electrochemical CO2 reduction reaction (ECO2RR) electrocatalyst for formate production. In this study, single‐crystalline Bi rhombic dodecahedrons (RDs) exposed with (104) and (110) facets are developed. The Bi RDs demonstrate a very low overpotential and high selectivity for formate production (Faradic efficiency >92.2%) in a wide partial current density range from 9.8 to 290.1 mA cm−2, leading to a remarkably high full‐cell energy efficiency (69.5%) for ECO2RR. The significantly reduced overpotential is caused by the enhanced *OCHO adsorption on the Bi RDs. The high selectivity of formate can be ascribed to the TSSs and the trivial surface states opening small gaps in the bulk gap on Bi RDs, which strengthens and stabilizes the preferentially adsorbed *OCHO and mitigates the competing adsorption of *H during ECO2RR. This study describes a promising application of Bi RDs for high‐rate formate production and high‐efficiency energy storage of intermittent renewable electricity. Optimizing the geometry of TCIs is also proposed as an effective strategy to tune the TSSs of topological catalysts.
The topological surface states and the trivial surface states opening small gaps in the bulk gap of Bi rhombic dodecahedrons facilitate highly selective formate production in a wide current density range, leading to a high full‐cell energy efficiency (maximum value of 69.5%) for electrochemical CO2 reduction reaction. This electrocatalyst can potentially be used for intermittent energy storage.
Abstract
Constructing stable electrodes which function over long timescales at large current density is essential for the industrial realization and implementation of water electrolysis. However, ...rapid gas bubble detachment at large current density usually results in peeling-off of electrocatalysts and performance degradation, especially for long term operations. Here we construct a mechanically-stable, all-metal, and highly active CuMo
6
S
8
/Cu electrode by in-situ reaction between MoS
2
and Cu. The Chevrel phase electrode exhibits strong binding at the electrocatalyst-support interface with weak adhesion at electrocatalyst-bubble interface, in addition to fast hydrogen evolution and charge transfer kinetics. These features facilitate the achievement of large current density of 2500 mA cm
−2
at a small overpotential of 334 mV which operate stably at 2500 mA cm
−2
for over 100 h. In-situ total internal reflection imaging at micrometer level and mechanical tests disclose the relationships of two interfacial forces and performance of electrocatalysts. This dual interfacial engineering strategy can be extended to construct stable and high-performance electrodes for other gas-involving reactions.
Durable and efficient hydrogen evolution reaction (HER) electrocatalysts that can satisfy industrial requirements need to be developed. Platinum (Pt)‐based catalysts represent the benchmark ...performance but are less studied for HER under high current densities in neutral electrolytes due to their high cost, poor stability, and extra water dissociation step. Here a facile and low‐temperature synthesis for constructing “blackberry‐shaped” Pt nanocrystals on copper (Cu) foams with low loading as self‐standing electrodes for HER in neutral media is proposed. Optimized hydrogen adsorption free energy and robust interaction induced by charge density exchange between Pt and Cu ensure the efficient and robust HER, especially under high current densities, which are demonstrated from both experimental and theoretical approaches. The electrode exhibits small overpotentials of 35 and 438 mV to reach current densities of ‐10 and ‐1000 mA cm−2, respectively. Meanwhile the electrode illustrates outstanding stability during chronoamperometry measurement under high current densities (‐100 to ‐400 mA cm−2) and 1000 cycles linear sweep voltammetry tests reaching ‐1000 mA cm−2. This study provides new design strategies for self‐standing electrocatalysts by fabricating robust metal–metal interactions between active materials and current collectors, thus facilitating the stable function of electrodes for HER under technologically relevant high current densities.
The facile in situ growth of blackberry‐shaped Pt nanocrystals on Cu foams as self‐standing hydrogen evolution reaction (HER) electrode is presented. The optimized hydrogen adsorption free energy and robust interaction between active materials and current collectors induced by charge density exchange ensure high efficiency and durability for HER in neutral media under technologically relevant high current densities.
A unique 3D flower-like zinc cobaltite (ZnCo2O4-x) with oxygen vacancies is designed and fabricated and a flexible solid-state ZIB was demonstrated, which delivers an extremely stable capacity under ...bending states.
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Aqueous zinc-ion batteries (ZIBs) are attracting considerable attention because of their low cost, high safety and abundant anode material resources. However, the major challenge faced by aqueous ZIBs is the lack of stable and high capacity cathode materials due to their complicated reaction mechanism and slow Zn-ion transport kinetics. This study reports a unique 3D ‘flower-like’ zinc cobaltite (ZnCo2O4-x) with enriched oxygen vacancies as a new cathode material for aqueous ZIBs. Computational calculations reveal that the presence of oxygen vacancies significantly enhances the electronic conductivity and accelerates Zn2+ diffusion by providing enlarged channels. The as-fabricated batteries present an impressive specific capacity of 148.3 mAh g−1 at the current density of 0.05 A g−1, high energy (2.8 Wh kg−1) and power densities (27.2 W kg−1) based on the whole device, which outperform most of the reported aqueous ZIBs. Moreover, a flexible solid-state pouch cell was demonstrated, which delivers an extremely stable capacity under bending states. This work demonstrates that the performance of Zn-ion storage can be effectively enhanced by tailoring the atomic structure of cathode materials, guiding the development of low-cost and eco-friendly energy storage materials.
Topological materials is one of the hottest topics in condensed matter physics because of its exotic properties such as robust metallic boundary states, Fermi arcs, and the spin‐momentum‐locking ...helicity. The topologically protected conducting boundary states spanning the whole bandgap are expected to serve as robust and wide‐range‐energy transition states facilitating catalytic reactions. Recently, some topological materials have been found to be high‐performance catalysts, which might open an emerging research field. Herein, an overview of topological materials is given and then recent progress in topological material catalysts (TMCs) is presented. As it is a new field, more detailed and accurate mechanisms behind the high performance of TMCs are urgently needed. Combining theoretical and experimental studies is a promising way to resolve these puzzles. Heterostructures, dopants, and defects have the chance to tune the catalytic activity of TMCs while retaining topological surface states (TSSs). Also, more TMCs are needed to be discovered, and more catalytic reactions are to be investigated for TMCs in the future.
Topological material catalyst (TMC) has shown exciting potential which might open an emerging research field. The progress, advantages, and challenges for TMC are presented in this Perspective. The main challenge is that the mechanism behind high performance is unclear. Topological surface state is supposed to be the key factor and possible methods to investigate it are put forward.
It remains a challenge to develop efficient electrocatalysts in neutral media for hydrogen evolution reaction (HER) due to the sluggish kinetics and switch of the rate determining step. Although ...metal phosphides are widely used HER catalysts, their structural stability is an issue due to oxidization, and the HER performance in neutral media requires improvement. Herein, a new material, i.e., grapevine‐shaped N‐doped iron phosphide on carbon nanotubes, as an efficient HER catalyst in neutral media is developed. The optimized catalyst shows an overpotential of 256 mV at a large current density of 65 mA cm−2, which is even 10 mV lower than that of the commercial 20% Pt/C catalyst. The excellent performance of the catalyst is further studied by combined computational and experimental techniques, which proves that the interaction between nitrogen and iron phosphides can provide more efficient active structures and stabilize the metal phosphide electrocatalysts for HER.
N‐doped FeP/carbon nanotube (CNT) grapevine‐shaped catalysts are successfully synthesized by a facile hydrothermal‐annealing method. The introduction of N can enhance the hydrogen evolution performance by optimizing electronic structure and stabilizing the structure of the material simultaneously under working condition. This work provides a facile method to stabilize metal phosphides for electrocatalysis process.
First-principle calculations of the electronic structure and magnetic interaction of C-Gd co-doped GaN nanowires have been performed. The room-temperature ferromagnetism in GaN:Gd nanowires is ...observed after the substitution of N atoms by C atoms. A p-d coupling is considered as the reason of the observed ferromagnetism. The striking feature is that such coupling is effected greatly by the position where the C atoms dope in. As the C-Gd distance increases this coupling decreases and the system won’t gain enough energy to stabilize the ferromagnetism.
Electronic and magnetic properties of Ga14N16−nGd2Cn monolayers are investigated by means of the first principle calculation. The generalized gradient approximation (GGA) of the density functional ...theory with the on-site Coulomb energy U was considered (GGA + U). It is found that the total magnetic moment of a Ga14N16Gd2 monolayer is 14 μB with an antiferromagnetic (AFM) phase. C atom substitutional impurity can effectively change the magnetic state of Ga14N16−nGd2Cn monolayers to ferromagnetic phases (FM), and the magnetic moment increases by 1μB/1C. The stable FM phase is due to the p-d coupling orbitals between the C-2p and Gd-5d states. Moreover, Curie temperature (TC) close to room temperature (TR, 300 K) is observed in the Ga14N16Gd2C2 monolayer, and the highest value can reach 261.46 K. In addition, the strain effect has a significant positive effect on the TC of the Ga14N16−nGd2Cn monolayer, which is much higher than the TR, and the highest value is 525.50 K. This provides an opportunity to further explore the application of two-dimensional magnetic materials in spintronic devices.
It is still a great challenge to achieve high selectivity of CH4 in CO2 electroreduction reactions (CO2RR) because of the similar reduction potentials of possible products and the sluggish kinetics ...for CO2 activation. Stabilizing key reaction intermediates by single type of active sites supported on porous conductive material is crucial to achieve high selectivity for single product such as CH4. Here, Cu2O(111) quantum dots with an average size of 3.5 nm are in situ synthesized on a porous conductive copper‐based metal–organic framework (CuHHTP), exhibiting high selectivity of 73 % towards CH4 with partial current density of 10.8 mA cm−2 at −1.4 V vs. RHE (reversible hydrogen electrode) in CO2RR. Operando infrared spectroscopy and DFT calculations reveal that the key intermediates (such as *CH2O and *OCH3) involved in the pathway of CH4 formation are stabilized by the single active Cu2O(111) and hydrogen bonding, thus generating CH4 instead of CO.
Cu2O(111) single‐type sites on a conductive metal–organic framework are successfully prepared by an in situ electrochemical method. The cooperative effect between the single active Cu2O(111) and hydrogen bonding contributes to the high selectivity of 73 % towards CH4 with large current density in CO2 electroreduction reduction for the obtained Cu2O(111)@CuHHTP.
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