The Nature of Structural Defects in ZIF-8 Revealed with H and P MAS NMR and X-Ray Absorption Spectroscopy.

The metal-organic frameworks (MOFs) attract interest as potential catalysts whose catalytic properties are driven by defects. Several methods have been proposed for the defects-inducing synthesis of MOFs. However, the active species formed on the defective sites remain elusive and uncharacterized, as the spectroscopic fingerprints of these species are hidden by the regular structure signals.

Correlating Single-Atomic Ruthenium Interdistance with Long-Range Interaction Boosts Hydrogen Evolution Reaction Kinetics.

Correlated single-atom catalysts (c-SACs) with tailored intersite metal-metal interactions are superior to conventional catalysts with isolated metal sites. However, precise quantification of the single-atomic interdistance (SAD) in c-SACs is not yet achieved, which is essential for a crucial understanding and remarkable improvement of the correlated metal-site-governed catalytic reaction kinetics. Here, three Ru c-SACs are fabricated with precise SAD using a planar organometallic molecular design and π-π molecule-carbon nanotube confinement.

Tuning Active Metal Atomic Spacing by Filling of Light Atoms and Resulting Reversed Hydrogen Adsorption-Distance Relationship for Efficient Catalysis.

Precisely tuning the spacing of the active centers on the atomic scale is of great significance to improve the catalytic activity and deepen the understanding of the catalytic mechanism, but still remains a challenge. Here, we develop a strategy to dilute catalytically active metal interatomic spacing (d) with light atoms and discover the unusual adsorption patterns. For example, by elevating the content of boron as interstitial atoms, the atomic spacing of osmium (d) gradually increases from 2.

Recent Progress in Metal-Catalyzed Selective Oxidation of 5-Hydroxymethylfurfural into Furan-Based Value-Added Chemicals.

5-hydroxymethylfurfural (HMF), one of the most significant biomass-derived renewable resources, has been widely utilized to create furan-based value-added chemicals such as 2,5-diformylfuran (DFF), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 5-formyl-2-furancarboxylic acid (FFCA), and 2,5-furan dicarboxylic acid (FDCA). Indeed, DFF, HMFCA and FFCA are key intermediate products during the oxidation of HMF to FDCA. Herein, this review aims to demonstrate the recent advances in metal-catalyzed oxidation of HMF into FDCA via two different reaction routes (HMF-DFF-FFCA-FDCA and HMF-HMFCA-FFCA-FDCA).

Metal Organic Framework Glasses: A New Platform for Electrocatalysis?

Metal organic framework (MOF) glasses are a coordination network of metal nodes and organic ligands as an undercooled frozen-in liquid, and have therefore broadened the potential of MOF materials in the fundamental research and application scenarios. On the road to deploying MOF glasses as electrocatalysts, it remains several basic scientific hurdles although MOF glasses not only inherit the structural merits of MOFs but also endow with active catalytic features including concentrated defects, metal centers and disorder structure etc. The research on the ionic conductivity, catalytic stability and reactivity of MOF glasses has yielded scientific insights towards its electrocatalytic applications.

Scalable Assembly of High-Quality Graphene Films via Electrostatic-Repulsion Aligning.

Assembling pristine graphene into freestanding films featuring high electrical conductivity, superior flexibility, and robust mechanical strength aims at meeting the all-around high criteria of new-generation electronics. However, voids and defects produced in the macroscopic assembly process of graphene nanosheets severely degrade the performance of graphene films, and mechanical brittleness often limits their applications in wide scenarios. To address such challenges, an electrostatic-repulsion aligning strategy is demonstrated to produce highly conductive, ultraflexible, and multifunctional graphene films.

Bridging sheet size controls densification of MXene films for robust electromagnetic interference shielding.

Numerous voids among the incompact layer-structure of MXene films result in their low ambient stability and poor innate conductivity for electromagnetic interference (EMI) shielding. Herein, we report a bridging-sheet-size-controlled densification process of MXene films by applying graphene oxide (GO) as a bridging agent. Specifically, the sheet size of GO is tailored to quantify a negative correlation of sheet size with densification for directing the preparation of most compact MXene-GO films.

Localizing Tungsten Single Atoms around Tungsten Nitride Nanoparticles for Efficient Oxygen Reduction Electrocatalysis in Metal-Air Batteries.

Combining isolated atomic active sites with those in nanoparticles for synergizing complex multistep catalysis is being actively pursued in the design of new electrocatalyst systems. However, these novel systems have been rarely studied due to the challenges with synthesis and analysis. Herein, a synergistically catalytic performance is demonstrated with a 0.

Ultrafast Macroscopic Assembly of High-Strength Graphene Oxide Membranes by Implanting an Interlaminar Superhydrophilic Aisle.

A macroscopic-assembled graphene oxide (GO) membrane with sustainable high strength presents a bright future for its applications in ionic and molecular filtration for water purification or fast force response for sensors. Traditionally, the bottom-up macroscopic assembly of GO sheets is optimized by widening the interlaminar space for expediting water passage, frequently leading to a compromise in strength, assembly time, and ensemble thickness. Herein, we rationalize this strategy by implanting a superhydrophilic bridge of cobalt-based metal-organic framework nanosheets (NMOF-Co) as an additional water "aisle" into the interlaminar space of GO sheets (GO/NMOF-Co), resulting in a high-strength macroscopic membrane ensemble with tunable thickness from the nanometer scale to the centimeter scale.

Dispersed FeO nanoparticles decorated with CoSiO hollow spheres for enhanced oxygen evolution reaction.

Oxygen evolution reaction (OER) has drawn ever-increasing attention because of its essential role in various renewable-energy technologies. In spite of tremendous research efforts, developing high-performance OER catalysts at low cost remains a great challenge. Inspired by two earth-abundant elements Fe and Si, herein, we report a Fe-CoSiO composite consisting of well dispersed iron oxide (FeO) decorated CoSiO hollow nanospheres as an economical and promising OER catalyst.

Manipulating Interfaces of Electrocatalysts Down to Atomic Scales: Fundamentals, Strategies, and Electrocatalytic Applications.

Raising electrocatalysis by rationally devising catalysts plays a core role in almost all renewable energy conversion and storage systems. The principal catalytic properties can be controlled and improved well by manipulation of interfaces, ascribed to the interactions among different components/players at the interfaces. In particular, manipulating interfaces down to atomic scales is becoming increasingly attractive, not only because those atoms at around the interface are the key players during electrocatalysis, but also, understandings on the atomic level electrocatalysis allow one to gain deep insights into the reaction mechanism.

Quench-Induced Surface Engineering Boosts Alkaline Freshwater and Seawater Oxygen Evolution Reaction of Porous NiCo O Nanowires.

The electrochemical oxygen evolution reaction (OER) by efficient catalysts is a crucial step for the conversion of renewable energy into hydrogen fuel, in which surface/near-surface engineering has been recognized as an effective strategy for enhancing the intrinsic activities of the OER electrocatalysts. Herein, a facile quenching approach is demonstrated that can simultaneously enable the required surface metal doping and vacancy generation in reconfiguring the desired surface of the NiCo O catalyst, giving rise to greatly enhanced OER activities in both alkaline freshwater and seawater electrolytes. As a result, the quenched-engineered NiCo O nanowire electrode achieves a current density of 10 mA cm at a low overpotential of 258 mV in 1 m KOH electrolyte, showing the remarkable catalytic performance towards OER.

A chainmail effect of ultrathin N-doped carbon shell on NiP nanorod arrays for efficient hydrogen evolution reaction catalysis.

Exploring innovation strategies has huge potential to significantly improving both activity and stability of current catalysts. Here, a chainmail design is proposed to enable the electronic interaction of ultrathin nitrogen-doped carbon shell with NiP nanorod core arrayed on nickel foam (NiP@NC/NF) for simultaneously promoting the activity and stability in both alkaline and neutral hydrogen evolution reaction (HER). The easy penetration of valence electrons from active NiP core to NC shell enables the obvious improvement of HER performance compared to pure NiP.

Electrospun One-Dimensional Electrocatalysts for Oxygen Reduction Reaction: Insights into Structure-Activity Relationship.

Oxygen reduction reaction (ORR) is an efficiency-determining process at the cathode in several energy storage and conversion devices, typically such as metal-air batteries and fuel cells. To date, a considerable amount of ORR electrocatalysts have been purposely exploited to address the key issues of high overpotentials and sluggish electrochemical kinetics. Electrospinning is a popular additive manufacturing technology, enabling the production of one-dimensional (1D) electrocatalysts with outstanding chemical stability and structural diversity.

Black Phosphorus@TiCT MXene Composites with Engineered Chemical Bonds for Commercial-Level Capacitive Energy Storage.

Electrolyte-accessibly porous yet densely packed MXene composite electrodes with high ion-accessible surface and rapid ion transport rate have shown exceptional promise for high-volumetric-performance supercapacitors (SCs), but they are largely limited by the insufficient rate capability and poor electrochemical cyclability, in association with the instability in mechanical robustness of the porous network structures. Taking advantage of chemical bonding design, herein a black phosphorus (BP)@MXene compact film of 3D porous network structure is successfully made by growth of BP nanoparticles on crumbled MXene flakes. The strong interfacial interaction (Ti-O-P bonds) formed at the BP-MXene interfaces not only enhances the atomic charge polarization in the BP-MXene heterostructures, leading to efficient interfacial electron transport, but also stabilizes the 3D porous yet dense architecture with much improved mechanical robustness.

Quasi-Paired Pt Atomic Sites on Mo C Promoting Selective Four-Electron Oxygen Reduction.

Atomically dispersed Pt species are advocated as a promising electrocatalyst for the oxygen reduction reaction (ORR) to boost noble metal utilization efficiency. However, when assembled on various substrates, isolated Pt single atoms are often demonstrated to proceed through the two-electron ORR pathway due to the unfavorable O─O bond cleavage thermodynamics in the absence of catalytic ensemble sites. In addition, although their distinct local coordination environments at the exact single active sites are intensively explored, the interactions and synergy between closely neighboring single atom sites remain elusive.

Electrocatalytically inactive copper improves the water adsorption/dissociation on NiS for accelerated alkaline and neutral hydrogen evolution.

Nickel dichalcogenides, especially Ni3S2, present inferior alkaline and neutral hydrogen evolution activity due to their sluggish water dissociation kinetics. Although these materials hold promise as non-noble metal-based electrocatalysts for the hydrogen evolution reaction (HER) in acidic media, developing efficient strategies to enhance the water dissociation processes of nickel dichalcogenides in alkaline and neutral solutions is also an important area of research. The present work discloses an electrocatalytically inactive copper doping strategy to promote the water adsorption and dissociation process of Ni3S2 (Cu-Ni3S2) nanoparticles supported on nickel foam (NF) towards improving the alkaline and neutral hydrogen evolution reactions.

Efficient Hydrogen Evolution of Oxidized Ni-N Defective Sites for Alkaline Freshwater and Seawater Electrolysis.

For mass production of high-purity hydrogen fuel by electrochemical water splitting, seawater electrolysis is an attractive alternative to the traditional freshwater electrolysis due to the abundance and low cost of seawater in nature. However, the undesirable chlorine ion oxidation reactions occurring simultaneously with seawater electrolysis greatly hinder the overall performance of seawater electrolysis. To tackle this problem, electrocatalysts of high activity and selectivity with purposely modulated coordination and an alkaline environment are urgently required.

Fiber-in-tube and particle-in-tube hierarchical nanostructures enable high energy density of MnO-based asymmetric supercapacitors.

Manganese dioxide (MnO) promises for high-performance asymmetric suprecapacitors, owing to its high theoretical capacity, abundant source, and low cost. However, insufficient practically-achievable capacity and relatively narrow voltage window in alkaline electrolyte are blocking high energy density of MnO-based supercapacitors, where strategies for activating its capacitive performance and widening voltage window are the top priorities to solve the bottleneck problems. Herein, both the fiber-in-tube (NCCM-FiT) and particle-in-tube (NCCM-PiT) nanostructures coulping active NiCoO nanoparticles and conductive carbon with MnO tubes have been purposely fabricated, using the electrospun nickel cobalt oxides/carbon nanofibers (NCO/CNFs) as the self-template agents for enhanced energy density of MnO-based supercapacitors.

Negative Pressure Pyrolysis Induced Highly Accessible Single Sites Dispersed on 3D Graphene Frameworks for Enhanced Oxygen Reduction.

Herein, we report a negative pressure pyrolysis to access dense single metal sites (Co, Fe, Ni etc.) with high accessibility dispersed on three-dimensional (3D) graphene frameworks (GFs), during which the differential pressure between inside and outside of metal-organic frameworks (MOFs) promotes the cleavage of the derived carbon layers and gradual expansion of mesopores. In situ transmission electron microscopy and Brunauer-Emmett-Teller tests reveal that the formed 3D GFs possess an enhanced mesoporosity and external surface area, which greatly favor the mass transport and utilization of metal sites.

Boosting Zn-Ion Storage Performance of Bronze-Type VO Ni-Mediated Electronic Structure Engineering.

Aqueous rechargeable zinc-ion batteries are emerging as attractive alternatives for post-lithium-ion batteries. However, their electrochemical performances are restricted by the narrow working window of materials in aqueous electrolytes. Herein, a Ni-mediated VO-B nanobelt [(Ni)VO] has been designed to optimize the intrinsic electronic structure of VO-B and thus achieve much more enhanced zinc-ion storage.

Synergizing Mo Single Atoms and Mo C Nanoparticles on CNTs Synchronizes Selectivity and Activity of Electrocatalytic N Reduction to Ammonia.

Previous research of molybdenum-based electrocatalysts for nitrogen reduction reaction (NRR) has been largely considered on either isolated Mo single atoms (MoSAs) or Mo carbide particles (e.g., Mo C) separately, while an integrated synergy (MoSAs-Mo C) of the two has never been considered.