Fe3 C/Fe Decorated N-doped Carbon Derived from Tetrabutylammonium tetrachloroferrate Complex as Bifunctional Electrocatalysts for ORR, OER and Zn-Air Batteries in Alkaline Medium.

The emergence of non-precious metal-based robust and economic bifunctional oxygen electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is crucial for the rational design of commercial rechargeable Zn-air batteries (RZAB) with safe energy conversion and storage systems. Herein, a facile strategy to fabricate a cost-efficient, bifunctional oxygen electrocatalyst Fe3 C/Fe decorated N doped carbon (FeC-700, the catalyst prepared at carbinization temperature of 700 °C) with a unique structure has been developed by carbonization of a single source precursor, tetrabutylammonium tetrachloroferrate(III) complex. The ORR and OER activity revealed excellent performance (ΔE=0.77 V) of the FeC-700 electrocatalyst, comparable to commercial Pt/C and RuO2, respectively. The designed temperature-tuneable structure provided sufficiently accessible active sites for the continuous passage of electrons by shortening the mass transfer pathway, leading to extremely durable electrocatalysts with high ECSA and amazing charge transfer performance. Remarkably, the assembled Zn-air batteries with the FeC-700 catalyst as the bifunctional air electrode delivers gratifying charging-discharging ability with an impressive power density of 134 mW cm-2 with a long lifespan, demonstrating prodigious possibilities for practical application.

Ni(II)-Incorporated Porphyrin-Based Conjugated Porous Polymer Derived from 2,6-Diformyl-4-methylphenol as a Catalyst for the Urea Oxidation Reaction.

The urea oxidation reaction (UOR) is an excellent alternative to the sluggish oxygen evolution reaction (OER) as an anode reaction for hydrogen generation via electrochemical water splitting. Here, a porphyrin-based conjugated porous polymer (CPP) has been developed through the polycondensation reaction of 2,6-diformyl-4-methylphenol and pyrrole (DMP-POR). The nickel(II) complex of this conjugated polymer Ni-DMP-POR shows efficient UOR in an alkaline medium. The as-synthesized materials were characterized by solid-state 13C CP-MAS, thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The porous property of the materials was characterized by N2 adsorption/desorption isotherms at 77 K. Both DMP-POR and Ni-DMP-POR showed excellent thermal stability. The Ni-DMP-POR exhibits very good UOR in 1 M KOH and 0.33 M urea with an overpotential of 260 mV at 10 mA cm-2 and a Tafel slope of 48 mV dec-1. The catalyst also shows excellent chronoamperometric and chronopotentiometric stability, suggesting its future scope in sustainable hydrogen production from wastewater resources.

A gold nanoparticle-intercalated mesoporous silica-based nanozyme for the selective colorimetric detection of dopamine.

Highly dispersed aggregation-free gold nanoparticles intercalated into the walls of mesoporous silica (AuMS) were synthesized using thioether-functionalized silica as a nanozyme, which exhibited an excellent peroxidase mimic activity. The AuMS material was characterized via XRD, N2 adsorption-desorption, FESEM, SEM-EDS particle mapping, TEM, and XPS. The peroxidase-like activity of the AuMS material was studied thoroughly, and the effect of pH and temperature was evaluated. The reproducibility of the peroxidase mimic activity and long-term stability of the AuMS catalyst were also studied. Furthermore, the AuMS catalyst was successfully utilized for the detection and quantification of dopamine, an important neurotransmitter, colorimetrically with a linear range of 10-80 µM and a limit of detection (LOD) value of 1.28 nM. The determination of dopamine concentration in commercially available dopamine hydrochloride injection showed high accuracy, good reproducibility, and high selectivity in the presence of uric acid, ascorbic acid, glucose, tryptophan, phenylalanine, and tyrosine.

One Step Synthesis of a Gold/Ordered Mesoporous Carbon Composite Using a Hard Template Method for Electrocatalytic Oxidation of Methanol and Colorimetric Determination of Glutathione.

Ordered mesoporous carbon-supported gold nanoparticles (Au/OMC) have been fabricated in one step through a hard template method using gold nanoparticle-intercalated mesoporous silica (GMS) to explore two different catalytic properties, for example, electrocatalytic oxidation of methanol and colorimetric determination of glutathione (GSH). The catalytically inert but conducting nature of mesoporous carbon (OMC) and promising catalytic activity of gold nanoparticles (AuNPs) has inspired us to synthesize Au/OMC. The as-prepared Au/OMC catalyst was characterized by powder X-ray diffraction, N2 adsorption-desorption, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray analysis-elemental mapping, and X-ray photoelectron spectroscopy. The characterization results indicate that AuNPs are uniformly distributed on the surface of OMC. The conducting-OMC framework with a high surface area of Au/OMC provides superior transport of electrons through the porous surface of carbon matrix and resulted in its high efficiency and stability as an electrocatalyst for the oxidation of methanol in comparison to CMK-3, SBA-15, and GMS in alkaline medium. The efficiency of Au/OMC toward methanol oxidation in alkaline medium is much higher in comparison to that in acidic medium. The lower value of I f/I b in the acidic medium in comparison to that in the alkaline medium clearly indicates that the oxidation process with Au/OMC as a catalyst is much more superior in alkaline medium with better tolerance toward the accumulation of intermediate CO species on the active surface area. Furthermore, the Au/OMC catalyst is successfully utilized for the detection and quantification of GSH spectrophotometrically with a limit of detection value of 0.604 nM.