Kousik Bhunia

A New Triazine-Based Covalent Organic Framework for High-Performance Capacitive Energy Storage

The new covalent organic framework material TDFP-1 was prepared through a solvothermal Schiff base condensation reaction of the monomers 1,3,5-tris-(4-aminophenyl)triazine and 2,6-diformyl-4-methylphenol. Owing to its high specific surface area of 651 m2  g-1 , extended π conjugation, and inherent microporosity, TDFP-1 exhibited an excellent energy-storage capacity with a maximum specific capacitance of 354 F g-1 at a scan rate of 2 mV s-1 and good cyclic stability with 95 % retention of its initial specific capacitance after 1000 cycles at 10 A g-1 . The π-conjugated polymeric framework as well as ionic conductivity owing to the possibility of ion conduction inside the micropores of approximately 1.5 nm make polymeric TDFP-1 a favorable candidate as a supercapacitor electrode material. The electrochemical properties of this electrode material were measured through cyclic voltammetry, galvanic charge-discharge, and electrochemical impedance spectroscopy, and the results indicate its potential for application in energy-storage devices.

Controlled Synthesis of CuS/TiO2 Heterostructured Nanocomposites for Enhanced Photocatalytic Hydrogen Generation through Water Splitting

Photocatalytic hydrogen (H2) generation through water splitting has attracted substantial attention as a clean and renewable energy generation process that has enormous potential in converting solar-to-chemical energy using suitable photocatalysts. The major bottleneck in the development of semiconductor-based photocatalysts lies in poor light absorption and fast recombination of photogenerated electron-hole pairs. Herein we report the synthesis of CuS/TiO2 heterostructured nanocomposites with varied TiO2 contents via simple hydrothermal and solution-based process. The morphology, crystal structure, composition, and optical properties of the as-synthesized CuS/TiO2 hybrids are evaluated in detail. Controlling the CuS/TiO2 ratio to an optimum value leads to the highest photocatalytic H2 production rate of 1262 μmol h-1 g-1, which is 9.7 and 9.3 times higher than that of pristine TiO2 nanospindles and CuS nanoflakes under irradiation, respectively. The enhancement in the H2 evolution rate is attributed to increased light absorption and efficient charge separation with an optimum CuS coverage on TiO2. The photoluminescence and photoelectrochemical measurements further confirm the efficient separation of charge carriers in the CuS/TiO2 hybrid. The mechanism and synergistic role of CuS and TiO2 semiconductors for enhanced photoactivity is further delineated.

Co(II)-Doped Cd-MOF as an Efficient Water Oxidation Catalyst: Doubly Interpenetrated Boron Nitride Network with the Encapsulation of Free Ligand Containing Pyridine Moieties

Development of an efficient and inexpensive water oxidation electrocatalyst using the earth-abundant elements is still far to go. Herein, a novel strategy has been demonstrated for developing the OER electrocatalyst by doping Co(II) in to a three-dimensional Cd-based MOF that contains a naked pyridine moieties in the form of uncoordinated ligand. Electrochemically active CoCd-MOF was resulted through the doping of Co(II) into the inactive Cd-MOF. CoCd-MOF exhibited very high catalytic activity in water oxidation reaction. An overpotential of 353 mV is required to produce an anodic current density of 1 mA/cm2 under alkaline conditions. Further, the CoCd-MOF exhibits remarkable recyclability over 1000 cycles.

Exposed Facets-Dependent Catalytic Properties of Nanocrystals: Noble Metals (Pd, Pt, and Au) and Oxides of First Row d-Block Elements

This review focuses on the recent progress in shape-controlled synthesis and exposed facets-dependent catalytic properties of widely used nanostructured noble metals (Pd, Pt, and Au), bimetallic alloys involving one noble metal, and oxides of first row d-block elements such as titanium oxide (TiO₂), vanadium oxide (V₂O5), chromium oxide (Cr₂O₃), manganese oxide (MnO₂), iron oxide (Fe₂O₃), cobalt oxide (Co₃O₄), nickel oxide (NiO), copper oxide (Cu₂O), and zinc oxide (ZnO). The major emphasis is given on the role of shape-controlling agents and experimental parameters to control the exposed facets of the nanocrystals. The importance of different high-index and high-energy exposed facets of noble metals and metal oxides with larger number of unsaturated atoms, edges, vertices, in different catalytic applications is presented. Furthermore, the synergy of both low-energy and high-energy exposed facets for efficient electron-hole separation for enhanced photocatalytic activity is discussed.