More than 95% (in volume) of all of today’s chemical products are manufactured through catalytic processes, making research into more efficient catalytic materials a thrilling and very dynamic rese...

Metal–Organic Frameworks in Heterogeneous Catalysis: Recent Progress, New Trends, and Future Perspectives

A comprehensive review of recent advances in the field of oxygen reduction electrocatalysis utilizing nonprecious metal (NPM) catalysts is presented Progress in the synthesis and characterization of pyrolyzed catalysts, based primarily on the transition metals Fe and Co with sources of N and C, is summarized Several synthetic strategies to improve the catalytic activity for the oxygen reduction reaction (ORR) are highlighted Recent work to explain the active-site structures and the ORR mechanism on pyrolyzed NPM catalysts is discussed Additionally, the recent application of Cu-based catalysts for the ORR is reviewed Suggestions and direction for future research to develop and understand NPM catalysts with enhanced ORR activity are provided

Nonprecious Metal Catalysts for Oxygen Reduction in Heterogeneous Aqueous Systems

Incorporating gold nanowires into scaffolds used to create heart patches can improve electrical communication between cells and enhance the growth of tissues.

Nanowired three-dimensional cardiac patches

The design and development of crystalline porous materials (CPMs), including metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs), have been subjects of extensive study due to their regular crystalline lattices and well-defined pore structures. In recent times, an enormous amount of research effort has gone into using CPMs as sacrificial templates to fabricate electrochemically functional materials. The inherently electrochemically active sites inside CPMs are notably abundant and being explored with respect to electrochemical reactions. In this review, electrochemically active sites and the space around them (metal ions, ligands, crystal structures, pores, and morphologies) inside CPMs are the focus and recent progress in the fields of metal-ion batteries, metal-air batteries, water splitting, and other related electrochemical devices has been summarized. Overall, this review provides guidance on the preparation of electroactive CPMs via rational design and modulation of active sites such as redox-active metal clusters and organic ligands, and the space around the electrochemically active sites, and their applications in electrochemical energy storage and conversion systems.

Electrochemically active sites inside crystalline porous materials for energy storage and conversion.

An advanced trifunctional electrocatalyst based on a series of composites composed of TiO2-encapsulated carbon-nitride (CNx) (denoted as TiO2C@CNx) is developed, which is derived from the Ti3C2Tx and melamine–cyanuric acid calcinated at different temperatures. Among the series of TiO2C@CNx nanosheets, the TiO2C@CNx,950 (obtained by calcination at 950 °C) hybrid exhibits robust trifunctional electrocatalytic activity toward the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) by combining the excellent electrochemical activity of the graphene-like nanostructure and the high electrocatalytic performances of TiO2 nanoparticles. When TiO2C@CNx,950 is used as the electrocatalyst for water splitting, a current density of 10 mA cm−2 (Ej = 10) is achieved at a low cell voltage of 1.50 V vs. reversible hydrogen electrode. Meanwhile, the overall oxygen activity of the TiO2C@CNx,950 exhibits good reversible oxygen reaction, giving a small potential difference between the Ej = 10 for OER and the half-wave potential for ORR (0.75 V). Moreover, a simply equipped Zn-air battery is assembled using a homemade cathode, showing open-circuit potential of 1.344 V, which also can supplied an electrical power and produced H2 at the cathode and O2 at the anode. Consequently, this work can pave a path for developing multifunctional electrocatalysts for water spitting and liquid Zn–air battery.

Titanium dioxide encapsulated carbon-nitride nanosheets derived from MXene and melamine-cyanuric acid composite as a multifunctional electrocatalyst for hydrogen and oxygen evolution reaction and oxygen reduction reaction

Editors’ Choice—Review—3D Printing: An Innovative Trend in Analytical Sensing

Lack of control over the structure and electrically nonconductive properties of coordination polymers (CPs) creates a major hindrance to designing an active electrocatalyst for oxygen reduction reaction (ORR). Here, we report a new semiconductive and low-optical band gap CP structure [{Co3(μ3-OH)(BTB)2(BPE)2}{Co0.5N(C5H5)}], 1, that exhibits high-performance ORR in alkaline medium. The electrical conductivity of compound 1 was measured using impedance spectroscopy and found to be 5 × 10–4 S cm–1. The Ketjenblack EC-600JD carbon used as a support for all the electrochemical methods such as cyclic voltammetry, rotating disk electrode, rotating ring-disk electrode and Koutecký–Levich analysis. The as-synthesized Co-based catalyst has the ability to reduce O2 to H2O by a nearly four-electron process. The crystal structure of 1 shows that the trimeric unit {Co3(μ3-OH)(COO)5N3} and monomeric unit {Co(COO)2(NC5H4)2}2+ are linked with BTB and BPE linkers to form a three-dimensional structure. Theoretical calculat...

Cobalt-Based Coordination Polymer for Oxygen Reduction Reaction.

Metal-Organic Complexes, [Co(bpy)3](NO3)2 and [Co(bpy)2NO3]NO3 · 5H2O, for Oxygen Reduction Reaction

Nitrogen Functionalized Few Layer Graphene Derived from Metal-Organic Compound: A Catalyst for Oxygen Reduction Reaction

A new, simple, green method for the synthesis of Au nanowires (average diameter 8 nm and several micrometers in length) using Au seeds prepared from bael gum (BG) is reported. The nanowires are characterized using UV–visible absorption spectroscopy, powder X-ray diffraction, transmission electron microscopy (TEM), and high-resolution-TEM. It is observed that the rate of the reduction process might be the decisive factor for the shape selectivity, as evident from the formation of nanowires at a particular concentration of seeds and NaOH. The polysaccharide present in BG is the active ingredient for the synthesis of Au nanowires, while the small molecules present in BG, when used alone, did not result in nanowire formation. The TEM images of the precursor to the Au nanowires suggested that new, nucleated particles align in a linear manner and fuse with one another, resulting in the nanowire. The linear fusion of the newly nucleated particles could be due to the lack of adequate protecting agent and the pres...

Anjaiah Sheelam

Papers

Editors’ Choice—Review—3D Printing: An Innovative Trend in Analytical Sensing

Cobalt-Based Coordination Polymer for Oxygen Reduction Reaction.

Metal-Organic Complexes, [Co(bpy)3](NO3)2 and [Co(bpy)2NO3]NO3 · 5H2O, for Oxygen Reduction Reaction

Nitrogen Functionalized Few Layer Graphene Derived from Metal-Organic Compound: A Catalyst for Oxygen Reduction Reaction

Green, Seed-Mediated Synthesis of Au Nanowires and Their Efficient Electrocatalytic Activity in Oxygen Reduction Reaction.