Khurram Saleem Joya

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

however, the design andimplementation of a stable and efficient molecular wateroxidation system that operates at high catalytic turnovernumber (TON) and frequency (TOF) for extended periods ofcontrolled-potential electrolysis (CPE), with moderate over-potential and high current density, are challenging.

Ab Initio Molecular Dynamics Study of Water Oxidation Reaction Pathways in Mono-Ru Catalysts

Ab initio molecular dynamics simulations with an adaptive biasing potential are carried out to study the reaction path in mononuclear Ru catalysts for water oxidation of the type [(Ar)Ru(X)(bpy)](+) with different aromatic ligands (Ar). The critical step of the O-O bond formation in the catalytic cycle starting from the [(Ar)Ru(O)(bpy)](2+) intermediate is analyzed in detail. It is shown that an explicit inclusion of the solvent environment is essential for a realistic description of the reaction path. Clear evidence is presented for a concerted reaction in which the O-O bond formation is quickly followed by a proton transfer leading to a Ru-OOH intermediate and a hydronium ion. An alternative path in which the approaching water first coordinates to the metal centre is also investigated, and it is found to induce a structural instability of the catalyst with the breaking of the aromatic ligand coordination bond.

Artificial Leaf Goes Simpler and More Efficient for Solar Fuel Generation

Layer upon layer: Solar-to-fuel conversion through water splitting is among the most challenging and growing fields in present day science. Herein, a report is highlighted that successfully demonstrates an efficient photoanodic system utilizing simple and low-cost tungsten-doped bismuth vanadate on single- or double-junction amorphous silicon photovoltaic in a tandem configuration.

Preparation and antibacterial properties of laser-generated silver?anatase nanocomposite film against Escherichia coli and Staphylococcus aureus

Anatase-based titanium dioxide (TiO(2)) naturally possesses a well recognized antibacterial effect under ultraviolet excitation. However, anatase modified with silver nanoparticles (Ag NPs) exhibits even stronger antibacterial action in natural daylight. The purpose of our present research is to evaluate the photocatalytic antibacterial effects of laser-generated silver-anatase nanocomposite film against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). A sol-gel TiO(2) precursor was spin-coated on a clean glass slide and silver ions were self-adsorbed from aqueous solution. A pulsed beam of KrF excimer laser (248 nm, 13 ns) was traversed over the amorphous film, leading to the crystallization of the anatase and formation of cubic as well as hexagonal Ag NPs. A scanning transmission electron microscope analysis revealed a 30-40 nm anatase crystallite size, whereas an average size of 9.6 nm was obtained from Ag NPs. The photo-absorption of plain anatase was red-shifted to 516 nm with the addition of Ag NPs after the laser treatment. Moreover, no colonies of E. coli and S. aureus cells were observed to survive after 60 min of contact with the laser-modified silver-anatase films in the dark and in daylight conditions.

Phase transformation and freestanding nanoparticles formation in lead zirconate titanate derived by sol-gel

Generation of the freestanding lead zirconate titanate (PZT) nanoparticles and their phase transformation behavior is investigated in this research. PZT sol-gel precursor was dried at 250°C and partially calcined at 450°C for 30min to decompose organics and bring down the free energy barrier for perovskite crystallization. Annealed at 550–600°C, sol-gel PZT powder exhibited freestanding nanocrystalline morphology. The electron diffraction pattern obtained from nanoparticles confirmed their crystallinity and perovskite phase formation. The structural characteristics were evaluated by transmission electron microscope and x-ray diffraction techniques. The average PZT nanoparticle size of 20nm was observed by transmission electron microscope and Scherrer’s method.

Comparative study of catalytic ozonation and Fenton-like processes using iron-loaded rice husk ash as catalyst for the removal of methylene blue in wastewater

ABSTRACT This study intends to compare the effectiveness of catalytic ozonation and Fenton-like processes for the decolorization of methylene blue using iron-loaded rice husk ash as catalyst. In both processes, effect of initial pH, adsorption, hydroxyl radical scavenger, and chemical oxygen demand removal was studied. The results revealed that catalytic processes were found to be pH dependent with the highest activity at pH 3.0. Unlike Fenton-like process, catalytic ozonation also found to be effective at pH 7.0. It is therefore, concluded that catalytic ozonation process is more effective than Fenton-like process near wastewater pH values.

Molecular Catalysts and Organometallics for Water Oxidation

Water can be used as a cheap and renewable source of electrons and protons to make nonfossil fuel-based chemical energy carriers for a sustainable power supply. However, water oxidation is an intricate chemical process and an energy-intensive reaction involving the removal of four electrons with the release of four protons at the same time. Inside the thylakoid membrane in plant leaves is embedded a manganese-calcium molecular cluster in natural photosystem II (PS-II), which represents an excellent model for designing an artificial equivalent of the photosynthesis for light-to-fuel conversion via water splitting. Inspired by the natural PS-II, the scientific community has been striving hard during the last two decades to develop a bio-inspired catalytic system for water oxidation. However, a truly biomimetic catalytic system matching the performance of photosystem for efficient water splitting operating with four consecutive proton-coupled electron transfer (PCET) steps to generate oxygen and hydrogen for hundred thousands of cycles at high rate is yet to be demonstrated. In this chapter, we provide an insight regarding the biomimetic approaches to make molecular and organometallic water oxidation complexes that have been investigated recently in homogeneous solution catalysis using chemical oxidants or as surface-immobilized heterogeneous species for electro-assisted catalytic systems. After comparing their catalytic activities and stabilities, an overview of the mechanistic aspects is also discussed.