Reinforcing the tetracene-based two-dimensional C48H16 sheet by decorating the Li, Na, and K atoms for hydrogen storage and environmental application -A DFT study.

To meet the increasing need of energy resources, hydrogen (H2) is being considered as a promising candidate for energy carrier that has motivated research into appropriate storage materials among scientists. Thus, in this study for the first time, zig-zag and armchair edged tetracene based porous carbon sheet (C48H16) is investigated for H2 storage using the density functional theory. To explore the hydrogen storage capacity, the hydrogen molecule is initially positioned parallel to the C48H16 sheet at three different sites, resulting in lower adsorption energies of -0.020, -0.024, and -0.015 eV respectively. The Li, Na, and K atoms are decorated to improve H2 adsorption on the C48H16 sheet. The Li atom decorated C48H16 sheet has a higher binding energy value of -2.070 eV than the Na and K atom decorated C48H16 sheet. The presence of Li, Na, and K atoms on the C48H16 sheet enhance the H2 adsorption energy than the H2 on the pristine C48H16 sheet. The decrease of Mulliken charge in alkali metal atoms (Li, Na, and K atom) on the C48H16 sheet reveal that the electron is transferred from H-σ orbital to s orbital of alkali metal atoms on the C48H16 sheet, leads to the enhancement of H2 binding. Compared to H2 adsorption on Na and K atom decorated C48H16 sheet, the H2 adsorption on Li atom decorated C48H16 sheet has the maximum adsorption energy value of -0.389 eV. The obtained hydrogen storage capacity of Li, Na, and K atoms decorated C48H16 sheets are about 7.49 wt%, 7.31 wt%, and 7.14 wt% respectively for four H2 molecules, which is greater than the targeted hydrogen storage capacity of the United States Department of Energy (DOE). Thus the obtained results in this work reveal that the decorated C48H16 sheets with Li, Na, and K atom plays the potential role in the H2 storage.

Non-noble metal (Ni, Cu)-carbon composite derived from porous organic polymers for high-performance seawater electrolysis.

The hydrothermal preparation of o-dianisidine and triazine interlinked porous organic polymer and its successive derivatisation via metal infusion (Ni, Cu) under hydrothermal and calcination conditions (700 °C) to yield pristine (ANIPOP-700) and Ni/Cu decorated porous carbon are described here (Ni-ANIPOP-700 and Cu-ANIPOP-700). To confirm their chemical and morphological properties, the as-prepared materials were methodically analyzed using solid state 13C and 15N NMR, X-ray diffraction, Raman spectroscopy, field emission scanning and high resolution transmission electron microscopic techniques, and x-ray photoelectron spectroscopy. Furthermore, the electrocatalytic activities of these electrocatalysts were thoroughly investigated under standard oxygen evolution (OER) and hydrogen evolution reaction (HER) conditions. The results show that all of the materials demonstrated significant activity in water splitting as well as displayed excellent stability (22 h) in both acidic (HER) and basic conditions (OER). Among the electrocatalysts reported in this study, Ni-ANIPOP-700 exhibited a lower overpotential η10 of 300 mV in basic medium (OER) and 150 mV in acidic medium (HER), as well as a lower Tafel slope of 69 mV/dec (OER) and 181 mV/dec (HER), indicating 30% lower energy requirement for overall water splitting. Gas chromatography was used to examine the electrolyzed products.

Facile fabrication of bifunctional SnO-NiO heteromixture for efficient electrocatalytic urea and water oxidation in urea-rich waste water.

Heterostructured transition metal oxide hybrid have more attention in energy saving and environmental related field due to their higher electro-catalytic activity. In this work, we demonstrated SnO decorated with NiO nanocrystal electrocatalyst is successfully synthesized through solvothermal method and well characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. Physical characterizations confirm that spherical shape of SnO nanoparticles are homogeneously dispersed on the surface of NiO. The kinetic study of catalytic performance towards urea oxidation reaction were measured by liner sweep voltammetry and chronoamprometry. As proposed catalyst to facilitate the rate of urea oxidation reaction can increase by SnO doped NiO catalyst. The urea oxidation on SnO-NiO nanostructured modified electrode exhibits lower onset potential of 1.12 V and enhancement of current with tafel slope of 150 mV dec-1. The obtained results demonstrated the synthesized SnO-NiO anode material could be promising electrode for urea-rich containing wastewater remediation and hydrogen production from wastewater.

MoS2 Decoration Followed by P Inclusion over Ni-Co Bimetallic Metal-Organic Framework-Derived Heterostructures for Water Splitting.

Demonstrating a highly efficient non-noble bifunctional catalyst for complete water electrolysis remains challenging because of kinetic limitations and crucial importance for future energy harvesting. Herein, a low-cost, integrated composite of a Ni-Co metal-organic framework decorated with thin MoS2 nanosheets was synthesized by a simple hydrothermal method followed by carbonization and phosphorization for electrochemical oxygen and hydrogen evolution reactions. Such a composite heterostructure exhibits outstanding performance in the electrocatalysis process with a lower overpotential of 184 mV for the oxygen evolution reaction (OER) and 84 mV for the hydrogen evolution reaction (HER) in 1.0 M KOH and 0.5 M H2SO4 electrolytes to reach a current density of 10 mA cm-2, with a slight Tafel slope of 63 mV dec-1 for the OER and 96 mV dec-1 for the HER. The obtained results are far better than those of the commercial benchmark catalyst. Furthermore, online gas chromatography quantifies the amount of hydrogen generation in a symmetric cell as equal to 0.002121 moles with an energy efficiency of about 2.237 mg/kWh. Thus, the composite electrode's remarkable performance is further demonstrated as a potentially viable alternative non-noble electrocatalyst for energy conversion reactions.

2D Trimetal-organic framework derived metal carbon hybrid catalyst for urea electro-oxidation and 4-nitrophenol reduction.

Because of the abundance of transition metals, their enhanced electrochemical/chemical efficiency on par with the benchmark catalysts, long-term stability, etc., the expansion of transition metal/metal oxide-based electrocatalysts for oxygen evolution, urea oxidation reactions and 4-nitrophenol reduction becomes indispensable. In particular, the abundant availability along with improved electrochemical performance is crucial for fuel cell applications when it comes to large scale commercialization. In this work, we report the synthesis of a trimetallic metal-organic framework based on Ni, Co and Zn using BTC as a linker and the preparation of its metal oxide - carbon composites at different temperatures, 600, 700 and 800 °C (TM-MOF-600, TM-MOF-700, and TM-MOF-800) by carbonization under an inert atmosphere. The PXRD pattern of TM-MOF complemented well with the simulated XRD patterns of Co-Ni-BTC MOF as well as Zn-BTC MOF, whereas the PXRD pattern of the carbonized samples indicated the presence of three types of metal oxides i.e., CoO, NiO, and ZnO. TEM indicated spherical morphology of TM-MOF, upon calcination, an irregular agglomeration occurred and the average particle size was found to be 60-110 nm. The as-prepared TM-MOF and its carbon composites were tested for their electrocatalytic as well as catalytic activities towards oxygen evolution, urea oxidation and 4-nitrophenol reduction reactions. Electrochemical results indicate the better performance of TM-MOF-800 in both OER and UOR reactions with an onset potential of 1.66 V (OER) and 1.37 V (UOR) at a current density of 10 mA cm-2. The long-term stability of these catalysts under alkaline conditions indicates excellent stability. Besides, the urea electrolyzed products were analyzed by gas chromatography to get clear insights on the formed products. Catalytic reduction of 4-nitrophenol in the presence of excess NaBH4 showed excellent conversion to 4-amino phenol in short duration.

Cobalt-modified 2D porous organic polymer for highly efficient electrocatalytic removal of toxic urea and nitrophenol.

The urea oxidation reaction (UOR) and nitrophenol reduction are safe and key limiting reactions for sustainable energy conversion and storage. Urea and nitrophenol are abundant in industrial and agricultural wastes, human wastewater, and in the environment. Catalytic oxidative and reductive removal is the most effective process to remove urea and 4-nitrophenol from the environment, necessary to protect human health. 2D carbon-supported, cobalt nanoparticle-based materials are emerging catalysts for nitrophenol reduction and as an anode material for the UOR. In this work, cobalt modified on a porous organic polymer (CoPOP) was synthesized and carbonized at 400 and 600 °C. The formation of CoPOP was confirmed by FT-IR spectroscopy, the 2D graphitic layer and amorphous carbon with cobalt metal by TEM, SEM, and PXRD, and the elemental composition by TEM mapping, EDX, and XPS. The catalytic activity for the 4-nitrophenol reduction was studied and the related electrocatalytic UOR was scientifically evaluated. The catalytic activity toward the reduction of 4-NP to 4-AP was tested with the addition of NaBH4; CoPOP-3 exhibited enhanced activity at a rate of 0.069 min-1. Furthermore, LSV investigated the catalytic activity of materials toward UOR, producing hydrogen gas, the products of which were analyzed via gas chromatography. Among the electrocatalysts studied, CoPOP-2 exhibited a lower onset potential, and the Tafel slope was 1.34 V and 80 mV dec-1. This study demonstrates that cobalt metal-doped porous organic polymers can be used as efficient catalysts to remove urea and nitrophenol from wastewater.

Electropolymerization of thienyl tethered comonomers and application towards the electrocatalytic reduction of nitrobenzene.

The synthesis of different π-spacered thiophene comonomers via Suzuki cross-coupling in good synthetic yields was accomplished. Potentiodynamic electropolymerization of these precursors on ITO electrode by constant potential electrolysis results in the deposition of thin films of polymers between 0.05 and 0.2 µM. Interestingly, the as synthesized π-conjugated polymers exhibit electrochromic behaviour upon electrochemical oxidation. On the application side, the synthesized electropolymers showed catalytic activity better than glassy carbon towards electrochemical reduction of nitrobenzene.

Porous Organic Polymer-Derived Carbon Composite as a Bimodal Catalyst for Oxygen Evolution Reaction and Nitrophenol Reduction.

Ethylene diamine-based porous organic polymer (EPOP) was synthesized, carbonized at different temperatures, and characterized. The successful formation of the triazine polymer was confirmed by Fourier-transform infrared spectroscopy, 13C, and 15N cross-polarization magic angle spinning solid-state NMR. The two-dimensional layered architecture and graphitic nature of the samples resembled that of nitrogen-doped amorphous carbon, as confirmed by Raman, powder X-ray diffraction, and transmission electron microscopy measurements. The catalytic activity of these materials toward nitrophenol reduction and electrocatalytic activity toward oxygen evolution reaction (OER) were systematically evaluated in detail. Electrocatalytic activity toward oxygen evolution reaction was systematically evaluated by chronoamperometry and linear sweep voltammetry. Results clearly demonstrate that all of these catalysts exhibit good OER activity and excellent stability. Among all catalysts, EPOP-700 showed better OER activity, as reflected by its onset potential and current density, comparable with that of the metal-based OER catalysts and better than that of metal-free catalysts. Further, their catalytic activity toward the reduction of 4-nitrophenol to 4-aminophenol was tested with NaBH4; although all of these catalysts showed good catalytic activity; EPOP-800 displayed better catalytic activity.

High Rate Performing in Situ Nitrogen Enriched Spherical Carbon Particles for Li/Na-Ion Cells.

Nitrogen rich, porous spherical carbon particle with the large surface area was synthesized by simple pyrolysis of the amorphous covalent organic framework. The obtained mesoporous spherical carbon particles with dilated interlayer distance (0.377 nm), large surface area (390 m2 g-1) and high level nitrogen doping (10.9%) offer eminent electrochemical performance as an anode for both lithium ion (LIBs) and sodium ion batteries (SIBs). In LIB applications, the synthesized material delivers an average reversible capacity of 820 mAh g-1 after 100 cycles at 0.1 A g-1, superior rate capability of 410 and 305 mAh g-1 at 4.0 and 8.0 A g-1 respectively. In SIBs, the material shows the stable reversible capacity of about 238 mAh g-1 for the studied 500 cycles at 0.5 A g-1. The rate and steady state cycling performance at high current densities are impressive, being as high as 165 mAh g-1 even after 250 cycles at 2.0 A g-1.