Search

The prevailing view about molecular catalysts is that the central metal ion is responsible for the reaction mechanism and selectivity, whereas the ligands mainly affect the reaction kinetics. Here, we question this paradigm and show that ligands have a dramatic influence on the selectivity of the product. We show how even a seemingly small change in ligand isomerization sharply alters the selectivity of the well‐researched oxygen reduction reaction (ORR) Co phthalocyanine catalyst from an indirect 2e− to a direct 4e− pathway. Detailed analysis reveals that intramolecular hydrogen‐bond interactions in the ligand activate the catalytic Co, directing the oxygen binding and thus deciding the final product. The resulting catalyst is the first example of a Co‐based molecular catalyst catalyzing a direct 4e− ORR via ligand isomerization, for which it shows an activity close to the benchmark Pt in an actual H2−O2 fuel cell. The effect of the ligand isomerism is demonstrated with different central metal ions, thus highlighting the generalizability of the findings and their potential to open new possibilities in the design of molecular catalysts. [ABSTRACT FROM AUTHOR]

The present work emphases on the post-mortem study of silica/carbon composite as functional anode in Li-ion batteries (LIBs). Herein, the silica/carbon composite is synthesized by facile in-situ hydrothermal technique. The x-ray diffraction (XRD) pattern indicates the amorphous nature of silica/carbon composite. The stacked sheet-like morphology of silica/carbon composite is seen in the high-resolution transmission electron microscopy (HR-TEM) & scanning electron microscopy (SEM) images. In addition, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, energy dispersive x-ray analysis (EDAX), and x-ray photoelectron spectra (XPS) characterizations of silica/carbon composite has been studied in detail. The rate capability of silica/carbon composite anode in LIB indicates 99% capacity retention after applying current density ranging from 50 mA g−1 to 1000 mA g−1, successively. The composite anode delivers a stable specific capacity ∼300 mAh g−1 at a current density of 100 mA g−1 for 500 cycles. Electrochemical impedance spectroscopy (EIS) study analyzed the faster Li-ion diffusion and increment in the diffusion coefficient by a factor of 1000 after 500 cycles. To the best of our knowledge, this is the first work on the post-mortem study of silica/carbon composite as anode in LIB. Post-cycling characterizations including XRD, FTIR, and SEM reveal the absence of any impurity phases and negligible volumetric expansion after prolonged cycling. It further confirms that the carbon present in the silica/carbon composite helps to accommodate the volumetric expansion of silica and prevents cracking of the anode over 500 cycles. [ABSTRACT FROM AUTHOR]

We demonstrate that the catalytic metal centre for ammonia production can be selectively activated with only a slight alteration in ligand isomerization (α and β isomers), making it practical and effective even for agricultural effluents. With almost 90% faradaic efficiency, the β isomer generates approximately 0.64 mg h−1 cm−2 of ammonia. Energy-efficient ammonia recovery is made possible by the interfacial proton charge assembly that β-isomerization creates, which attracts the reacting nitrate and repels the competing hydronium ions. With minimal energy consumption, this isomerization approach can interconvert agricultural effluents into ammonia fuel, reaching up to 84% of its theoretical yield and maintaining stability over 100 hours of continuous electrolysis. [ABSTRACT FROM AUTHOR]

Direct urea fuel cells (DUFCs) offer an environmentally friendly, and cost-effective way to turn wastewater into energy. However, the paucity of efficient, cost-effective, and electrochemically stable urea electro-oxidation reaction (UOR) specific electrocatalysts continues to impede the design and development of practically useful DUFCs. The present work explores the design and development of N-doped graphene (NGr)-supported platinum (Pt) plus silver (Ag) alloy nanohybrids (PtxAg100−x-NGr) as potential UOR electrocatalysts. Our results suggest that the electrocatalytic performance of PtxAg100−x-NGr is very sensitive toward the composition of this nanohybrid. The nanohybrid with a Pt : Ag ratio of 1 : 1, referred to as Pt50Ag50-NGr in the MS, exhibits the best UOR electrocatalytic performance. The Pt50Ag50-NGr composite exhibits a Tafel slope of just ∼12.92 mV dec−1, and a UOR-specific activity of nearly 4028 mA cm−2 mg cat−1 at 1.673 V (vs. RHE) and requires an overpotential of just 1.617 V (vs. RHE) to maintain a UOR specific current density of 10 mA cm−2. These parameters qualify the Pt50Ag50-NGr as a promising anode material for DUFCs. This we demonstrate through the design of a Pt50Ag50-NGr anode-based prototype urea-H2O2 fuel cell that delivers an open circuit voltage (OCV) of 750 mV and a power density of ∼5.75 mW cm−2. [ABSTRACT FROM AUTHOR]

Introducing novel functionalities to state-of-the-art batteries has the potential to immensely enrich energy conversion chemistry. Here, we show a Zn-air battery concept wherein pollutant degradation is paired with electric power production facilitated by the in situ transformation of hydrogen peroxide (H2O2) produced on battery discharge to extremely reactive hydroxyl (˙OH) radical via Fenton's reaction. The battery delivered an open circuit voltage of nearly 1.3 V, a peak power density of nearly 55 mW cm−2 at a peak current density of ∼125 mA cm−2, while simultaneously degrading pollutants such as Acetaminophen and phenol during the delivery of electric power. The ability of batteries to couple pollutant degradation with electric power delivery adds a novel dimension to their chemistry to perform challenging tasks in the sustainable energy landscape. [ABSTRACT FROM AUTHOR]

Development of miniaturized lab‐on‐chip devices for the detection of rapid and specific small molecule‐protein binding interactions at very low concentrations holds significant importance in drug discovery and biomedical applications. Here, the label‐free detection of small molecule‐protein interactions is reported on the surface functionalizable nanotubes of α,γ‐hybrid peptide helical foldamers using nanoscale capacitance and impedance spectroscopy. The 12‐helix conformation of the α,γ‐hybrid peptide observed in the single crystals, self‐assembled into nanotubes in an aqueous environment with exposed cysteine thiols for small molecule conjugation. The binding of streptavidin to the covalently linked biotin on the surface of nanotubes was detected at the picomolar concentrations. No change in the capacitance and impedance were observed in the absence of either immobilized biotin or protein streptavidin. The functionalizable hybrid peptide nanotubes reported here pave the way for the label‐free detection of various small molecule protein interactions at very low concentrations. [ABSTRACT FROM AUTHOR]

Aqueous Zn‐based batteries hold multiple advantages of eco‐friendliness, easy accessibility, high safety, easy fabrication, and fast kinetics, while their widespread applications have been greatly limited by the relatively narrow thermodynamically stable potential windows (i. e. 1.23 V) of water and the mismatched pH conditions between cathode and anode, which presents challenges regarding how to maximize the output voltage and the energy density. Recently, aqueous OH−/H+ dual‐ion Zn‐based batteries (OH−/H+‐DIZBs), where the Zn anode reacts with hydroxide ions (OH−) in alkaline electrolyte while hydrogen ions (H+) are involved in the cathode reaction in the acidic electrolyte, have been reported to be capable of broadening the working voltage and improving the energy density, which offers practical feasibility toward overcoming the above limitations. This Review thus takes this chance to investigate the recent progress on aqueous OH−/H+‐DIZBs. First, the concept and the history of such OH−/H+‐DIZBs are introduced, and then special emphasis is put on the working mechanisms, the progress of the development of new batteries, and how the electrolytes improve their performance. Finally, the challenges and opportunities in this field are discussed. [ABSTRACT FROM AUTHOR]

In the present work, we have demonstrated the synthesis of Molybdenum Carbide‐reduced graphene oxide (Mo2C‐rGO) heterostructure. Uniquely, the in‐situ formation of rGO using D‐glucose in the heterostructure and its battery performance has been discussed. The High Resolution Transmission Electron Microscopy (HR‐TEM) study clearly shows the growth of Mo2C nanoparticles along with rGO confers a unique integrated layered heterostructure. X‐ray diffraction (XRD) and Raman study exhibits the formation of graphene oxide (GO) followed by multi‐layers of rGO along with hexagonal Mo2C. The electrochemical study of Mo2C‐rGO heterostructure demonstrates stable cycling performance and excellent rate capabilities. The heterostructure showed the initial capacity (1st discharge) around 632.23 mAh/g and specific capacity i. e., 537.91 mAh/g @ 0.5 A/g with 99–100 % columbic efficiency. The reversible capacities of 521.56 mAh/g, and 400.76 mAh/g were observed at current densities of 1 A/g and 2 A/g for 300 cycles, respectively, which justifies the stability of heterostructure. The cycled cell was investigated by using Electrochemical Imepedance Spectroscopy (EIS), ex‐situ XRD, and Field Emmision Scanning Electron microscopy (FESEM), which shows the negligible change in the ionic conductivity, structure, and morphology after 300 cycles. It shows the excellent stability of Mo2C‐rGO heterostructure. [ABSTRACT FROM AUTHOR]

Electrocarboxylation of halocarbons is a promising green synthetic strategy for capture, fixation and utilization of CO2 for the synthesis of high-added-value industrial compounds. However, the unparalleled kinetic/thermodynamic stability and solubility concerns of CO2 and halocarbons warrant the use of appropriate (often precious metal based) electrocatalytic electrodes and environmentally non-green solvent systems to drive this otherwise kinetically slow electrochemical process. Herein we demonstrate that owing to their unique solubility and excellent electrocatalytic properties, the aqueous micellar solutions of imidazolium-based surface active ionic liquids (SAILs) can be used for the efficient and selective electrocatalytic-carboxylation of halocarbons to produce carboxylic acids. Specifically, we present results from our detailed electrochemical investigations regarding the electroreductive cleavage of the C–X bond and electrocarboxylation of 9-bromoanthracene (9-BAN) and chloroacetonitrile (CAN) in buffered (pH 7, phosphate buffer) micellar solutions of 1-dodecyl-3-methyl-imidazolium chloride ([DDMIM][Cl]). We demonstrate that the unique ability of [DDMIM][Cl] micelles to stabilize the electrogenerated reactive intermediates facilitates a novel reaction pathway that ensures selective and efficient electrocatalytic-reductive carboxylation of 9-BAN and CAN. The presented results clearly establish that besides allowing for the electrocarboxylation of halocarbons in aqueous green electrolytes, the use of SAILs ensures electrochemical fixation of CO2 at practically low cost current and potential conditions imposed over metal free, economically viable and electrochemically robust carbon electrodes. The use of SAILs is reported to improve the faradaic efficiency (∼95%) and reduce the chances of undesired side product reactions which continue to be a major concern in the state of art electro-carboxylation processes. The presented approach we opine offers a promising avenue toward design of eco-green pathways in the direction of CO2 fixation and electro-organic synthesis of a diverse range of value-added products from water insoluble halocarbons (toxic pollutants) in aqueous media. [ABSTRACT FROM AUTHOR]