To restore the natural nitrogen cycle (N-cycle), artificial N-cycle electrocatalysis with flexibility, sustainability, and compatibility can convert intermittent renewable energy (e.g., wind) to harmful or value-added chemicals with minimal carbon emissions. The background of such N-cycles, such as nitrogen fixation, ammonia oxidation, and nitrate reduction, is briefly introduced here. The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design, electrochemical performances, reaction mechanisms, and instructive tests. Energy device advancements for achieving more functions as well as <i>in situ</i>/<i>operando</i> characterizations toward understanding key steps are also highlighted. Furthermore, some recently proposed reactions as well as less discussed C–N coupling reactions are also summarized. We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types, namely, abundant nitrogen, toxic nitrate (nitrite), and nitrogen oxides, and useful compounds such as ammonia, hydrazine, and hydroxylamine, with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy. 

https://www.sciopen.com/article_pdf/1531201054523838466.pdf

Recent advances in nanostructured heterogeneous catalysts for N-cycle electrocatalysis

Polyoxometalates (POMs) represent a class of nanomaterials, which hold enormous promise for a range of energy-related applications. Their promise is owing to their “special” structure that gives POMs a truly unique ability to control redox reactions in energy conversion and storage. One such amazing capability is their large number of redox active sites that arises from the complex three-dimensional cluster of metal-oxide ions linked together by oxygen atoms. Here, a critical review on how POMs emerged from being molecular clusters for fundamental studies, to next-generation materials for energy applications is provided. We highlight how exploiting the versatility and activity of these molecules can lead to improved performance in energy devices such as supercapacitors and batteries, and in energy catalyst applications. The potential of POMs across numerous fields is systematically outlined by investigating structure–property–performance relationships and the determinant factors for energy systems. Finally, the challenges and opportunities for this class of materials with respect to addressing our pressing energy-related concerns are identified.

Polyoxometalates (POMs): from electroactive clusters to energy materials

Improving the photocatalytic H2 evolution activity of Keggin polyoxometalates anchoring copper-azole complexes

FeS2/MoS2@RGO hybrid materials derived from polyoxomolybdate-based metal–organic frameworks as high-performance electrocatalyst for ammonia synthesis under ambient conditions

Two-dimensional (2D) metal–organic frameworks (MOFs) serve as emerging electrocatalysts due to their high conductivity, chemical tunability, and accessibility of active sites. We herein proposed a series of 2D MOFs with different metal atoms and organic linkers with the formula M3C12X12 (M = Cr, Mo, and W; X = NH, O, S, and Se) to design efficient nitrogen reduction reaction (NRR) electrocatalysts. Our theoretical calculations showed that metal atoms in M3C12X12 can efficiently capture and activate N2 molecules. Among these candidates, W3C12X12 (X = O, S, and Se) show the best NRR performance due to their high activity and selectivity as well as low limiting potential (−0.59 V, −0.14 V, and −0.01 V, respectively). Moreover, we proposed a d-band center descriptor strategy to screen out the high activity and selectivity of M3C12X12 for the NRR. Therefore, our work not only demonstrates a class of promising electrocatalysts for the NRR but also provides a strategy for further predicting the catalytic activity of 2D MOFs.

Design strategies of two-dimensional metal-organic frameworks toward efficient electrocatalysts for N2 reduction: cooperativity of transition metals and organic linkers.

Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

The invention relates to the construction of an electrochemical sensor used for detecting glucose. The invention provides a novel construction material NiFe2O4-NiCo-LDH@GO of an electrochemical glucose sensor. A simple and environment-friendly synthesis method is adopted for preparing the composite material, and an electrochemical approach is utilized to detect glucose. The linear response range of the prepared sensor for glucose is 3.5*10 -4.525*10 M, the sensitivity is 7.897 microamperes/milliamperes, and the detection limit is 12.94*10 M. The electrochemical sensor has the advantages of simple and convenient operation, low cost and excellent anti-interference capability and can quickly and effectively detect glucose in human serum.

Electrochemical sensor used for detecting glucose

The invention discloses a Keggin type cobalt tungstate cobalt coordination polymer and a synthesis method and application thereof, belongs to the technical field of preparation of coordination polymers, and aims to solve the technical problems of high-dissolubility instability and poor conductivity of polyacid electrode materials in a water solution. The molecular formula of the polymer is W36Co11O144C24N48H98. The synthesis method comprises the following steps: placing 4-amino-4H-1,2,4-triazole, cobalt nitrate, K8Co2W11O40H2.15H2O in distilled water of 5-10 ml, stirring at room temperature until the mixture is evenly mixed, adjusting the pH value of the system to 2-5, putting the mixture into a stainless steel reaction kettle lined with polytetrafluoroethylene, reacting at 120-160 DEG C for 3-5 days, and cooling to room temperature to obtain the Keggin type cobalt tungstate cobalt coordination polymer. The polymer can be used as a polyacid-based metal organic super capacitor material.The Keggin type cobalt tungstate cobalt coordination polymer is applied to the preparation field of polyacid-based inorganic organic energy storage materials.

Keggin type cobalt tungstate cobalt coordination polymer and synthesis method and application thereof

The invention discloses preparation and capacitive performance of a three-dimensional cobalt tungstate-based nickel organic framework material and aims to design and synthesize a three-dimensional network structure which is constructed by an organic structural unit of binuclear metal Ni2(C2N4H4)3 and CoW12 polyoxometalate anions provided with four connection points respectively. The provided polyoxometalate-based metal organic framework material contains nickel, cobalt and tungsten, and contribution is made for solving the problem of monotonous active sites of conventional electrode materials.A three-dimensional polyoxometalate-based nickel metal-organic crystalline state energy storage material is designed by means of a one-step hydrothermal synthesis method, wherein the molecular formula of the material is H5[CoW12O40]3[Ni2(OH)3]4[C2N4H4]12 12H2O, and the crystal system is a cubic crystal system; according to the cell parameters, alpha is equal to 90, beta is equal to 134.956, gammais equal to 90, a is equal to 35.770(5) , b is equal to 25.305(5) , c is equal to 25.293(5) , and Z is equal to 1. The preparation method comprises the steps of dissolving a metal nickel salt, K8Co2W11O40H2 15H2O, C4, ammonium metavanadate and triethylamine, and then adjusting the pH; triggering a reaction of a reactive solution at 160 DEG C, and then cooling the reactive solution to the room temperature. The three-dimensional polyoxometalate-based nickel metal-organic crystalline state energy storage material can be obtained through the method.

Feng Zemin

Papers

Polyoxometalate-based metal–organic framework-derived bimetallic hybrid materials for upgraded electrochemical reduction of nitrogen

Electrochemical sensor used for detecting glucose

Keggin type cobalt tungstate cobalt coordination polymer and synthesis method and application thereof

Preparation and capacitive performance of three-dimensional cobalt tungstate-based nickel organic framework material