Recent advances in non-noble metal electrocatalysts for nitrate reduction

Rechargeable Zn-air batteries are under intensive studies because of their high-energy density, low cost, and safety. However, their wide application is prevented by several remaining technical issues, one of which is the lack of suitable bifunctional cathodic catalysts for oxygen reduction reaction (ORR) during discharging and oxygen evolution reaction (OER) during charging. Due to low material cost and wide distribution, carbon-based materials may serve as promising electrocatalysts, while doping heteroatoms such as nitrogen or boron can effectively enhance their catalytic activity. Herein, we pyrolyze a metal-organic framework containing Zn, N, and B as the precursor to synthesize dual-doped and metal-free porous carbon materials as efficient ORR/OER bifunctional electrocatalysts. The surface area of obtained carbon materials can be greatly enhanced by pyrolysis under H 2 -containing atmosphere. In addition, N and B are evenly distributed within the carbon materials due to the crystalline MOF precursor. The resultant carbon materials exhibit high ORR and OER catalytic activities in both half-cell and single-cell battery measurements. Our study has demonstrated for the first time that MOFs can be used as precursors to synthesize metal-free ORR/OER bifunctional cathodic electrocatalysts with great potential in rechargeable Zn-air batteries.

A metal-free ORR/OER bifunctional electrocatalyst derived from metal-organic frameworks for rechargeable Zn-Air batteries

MOF based engineered materials in water remediation: Recent trends.

Bifunctional Bi12O17Cl2/MIL-100(Fe) composites toward photocatalytic Cr(VI) sequestration and activation of persulfate for bisphenol A degradation.

MXene combining high metal-like conductivity, high hydrophilicity, and abundant surface functional groups has been recognized as a class of versatile two-dimensional materials for many applications. However, the aggregation of MXene nanosheets from interlayer van der Waals force and hydrogen bonds represents a major problem that severely limits their practical use. Here, we report an aerogel structure of MOFs@MXene, in which the in situ formed MOF particles can effectively prevent the accumulation of MXene, enabling a three-dimensional (3D) hierarchical porous conductive network to be composed with an ultralight feature. Subsequently, a 3D porous MXene aerogel threaded hollow CoS nanobox composite ((CoS NP@NHC)@MXene) derived from the MOFs@MXene aerogel precursor was synthesized, and the highly interconnected MXene network and hierarchical porous structure coupled with the ultrafine nanocrystallization of the electrochemically active phase of CoS yield the hybrid system with excellent electron and ion transport properties. Benefiting from the synergistic effect of the components, the (CoS NP@NHC)@MXene composite manifests outstanding electrochemistry properties as electrode materials for all of the lithium-ion batteries (LIBs), sodium-ion batteries (SIBs), and potassium-ion batteries (PIBs). It demonstrated the excellent cycle stability and high capacities of 1145.9 mAh g-1 at 1 A g-1 after 800 cycles and 574.1 mAh g-1 at 5 A g-1 after 1000 cycles for LIBs, 420 mAh g-1 at 2 A g-1 after 650 cycles for SIBs, and 210 mAh g-1 at 2 A g-1 after 500 cycles for PIBs. First-principle calculations confirmed that the (CoS NP@NHC)@MXene hybrid could enhance the charge transfer reaction kinetics, particularly at the interface. More importantly, the excellent rate performance under high mass loading and the high volumetric energy and power density of the entire electrode represent the potential of (CoS NP@NHC)@MXene composites for applications to practical electrochemical energy storage devices. The synthesis method reported in this Article is versatile and can be easily extended to produce other porous MXene-aerogel-based materials for various applications.

Three-Dimensional MOFs@MXene Aerogel Composite Derived MXene Threaded Hollow Carbon Confined CoS Nanoparticles toward Advanced Alkali-Ion Batteries.

Metal–organic frameworks (MOFs) are a special class of porous materials and have been widely explored for applications in supercapacitors, catalysts, and adsorbents, because of their large specific surface areas and tunable structure and composition. However, traditional MOFs suffer from poor conductivity and low stability, which limit their efficiency in catalysis and other applications that require good electrical conduction. To overcome this limitation, a composite made of electrically conducting graphene and MOFs is conceptually a viable solution. This review summarizes the latest preparation methods for MOF/graphene materials with a focus on applications in electrocatalysis and photocatalysis. We aim to assist existing researchers to obtain a fast and holistic overview of MOF and their derivatives with graphene composites in catalysis, and also the new comers to quickly catch up with the latest development in this field.

Metal–organic frameworks and their derivatives with graphene composites: preparation and applications in electrocatalysis and photocatalysis

Sluggish kinetics of the multielectron transfer process is still a bottleneck for efficient oxygen evolution reaction (OER) activity, and the reduction of reaction overpotential is crucial to boost reaction kinetics. Herein, a correlation between the OER overpotential and the cobalt-based electrode composition in a "Microparticles-in-Spider Web" (MSW) superstructure electrode is revealed. The overpotential is dramatically decreased first and then slightly increased with the continuous increase ratio of Co/Co3 O4 in the cobalt-based composite electrode, corresponding to the dynamic change of electrochemically active surface area and charge-transfer resistance with the electrode composition. As a proof-of-concept, the optimized electrode displays a low overpotential of 260 mV at 10.0 mA cm-2 in alkaline conditions with a long-time stability. This electrochemical performance is comparable and even superior to the most currently reported Co-based OER electrocatalysts. The remarkable electrocatalytic activity is attributed to the optimization of the electrochemically active sites and electron transfer in the MSW superstructure. Theoretical calculations identify that the metallic Co and Co3 O4 surface catalytic sites play a vital role in improving electron transport and reaction Gibbs free energies for reducing overpotential, respectively. A general way of boosting OER kinetics via optimizing the electrode configurations to mitigate reaction overpotential is offered in this study.

Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the “Microparticles-in-Spider Web” Electrode Configurations

Oxygen Evolution Reaction Kinetics: Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the “Microparticles-in-Spider Web” Electrode Configurations (Small 8/2020)

The invention discloses a method for rapidly preparing green MOFs (Metal-organic frameworks) porous microspheres. The method comprises the steps: adding a first polymer to a solvent, and stirring andmixing at room temperature to obtain a mixed solution I; adding MOFs to the mixed solution I, and then stirring and mixing at room temperature to obtain a mixed solution II; ultrasonically oscillatingthe mixed solution II uniformly, and then obtaining the green MOFs porous microspheres by electrospinning treatment. The method disclosed by the invention has the advantages that the preparation process is simple, safe and controllable, less time and energy are consumed, and the cubic crystal type MOFs are converted into the MOFs porous microspheres by electrospinning. Most importantly, in the process of preparing the MOFs porous microspheres, no contaminating heavy metals or toxic substances are used, and no pollution is caused.

Qi Guo

Papers

Metal–organic frameworks and their derivatives with graphene composites: preparation and applications in electrocatalysis and photocatalysis

Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the “Microparticles-in-Spider Web” Electrode Configurations

Oxygen Evolution Reaction Kinetics: Reducing Oxygen Evolution Reaction Overpotential in Cobalt-Based Electrocatalysts via Optimizing the “Microparticles-in-Spider Web” Electrode Configurations (Small 8/2020)

Method for rapidly preparing green MOFs (Metal-organic frameworks) porous microspheres