Photo-driven Reaction Research Articles

QRCODE: Massively parallelized real-time time-dependent density functional theory for periodic systems

We present a new software module, QRCODE (Quantum Research for Calculating Optically Driven Excitations), for massively parallelized real-time time-dependent density functional theory (RT-TDDFT) calculations of periodic systems in the open-source Qbox software package. Our approach utilizes a custom implementation of a fast Fourier transformation scheme that significantly reduces inter-node message passing interface (MPI) communication of the major computational kernel and shows impressive scaling up to 16,344 CPU cores. In addition to improving computational performance, QRCODE contains a suite of various time propagators for accurate RT-TDDFT calculations. As benchmark applications of QRCODE, we calculate the current density and optical absorption spectra of hexagonal boron nitride (h-BN) and photo-driven reaction dynamics of the ozone-oxygen reaction. We also calculate the second and higher harmonic generation of monolayer and multi-layer boron nitride structures as examples of large material systems. Our optimized implementation of RT-TDDFT in QRCODE enables large-scale calculations of real-time electron dynamics of chemical and material systems with enhanced computational performance and impressive scaling across several thousand CPU cores.

Light-Driven De/Rehydrogenation of a LiH Surface under Ambient Conditions.

Lithium hydride (LiH), a saline hydride with a hydrogen density of 12.6 wt %, is highly thermostable, which hinders its extensive application in hydrogen storage. In this study, we demonstrate a distinct photodecomposition of LiH under ambient conditions. Ultraviolet-visible (UV-vis) illumination induces hydrogen release and creates surface hydrogen vacancies on LiH. The subsequent H- migration enables hydrogen desorption and the accumulation of vacancies at the subsurface, resulting in the generation of metallic Li clusters. Rehydrogenation, on the contrary, can be charged under UV-vis illumination in 1 bar H2. Such phenomena show that the thermodynamic and kinetic limits in the re/dehydrogenation of LiH can be broken under illumination, which allows hydrogen storage over the LiH surface at temperatures ∼600 K lower than those of the corresponding thermal process. This work provides new insights into the interaction of semiconducting hydrides and photons and opens an avenue for the development and optimization of materials for hydrogen storage and related photodriven reactions.

Interfacial charge transfer complexes between ZnO and benzene derivatives: Characterization and photocatalytic hydrogen production

The interfacial charge transfer (ICT) complex formation is a simple procedure to bring optical absorption of wide-bandgap oxide materials in the visible spectral range, crucial for enhancing their use in photo-driven reactions. The optical absorption of the prepared ICT complexes between ZnO and five different colorless benzene derivatives is red-shifted compared to pristine ZnO nanopowder. The density functional theory (DFT) calculations provided realistic energy level alignment in hybrid systems. Also, the DFT-calculated infrared spectra support the binding structures derived based on experimental measurements of free and adsorbed ligands onto ZnO surfaces. The photocatalytic performance of prepared hybrids was evaluated using photocatalytic hydrogen generation in the water-splitting reaction. The ZnO nanopowders modified with catechol and caffeic acid have over 50% higher hydrogen production rate than pristine ZnO, displaying steady hydrogen production under long-run working conditions.

Investigations of photo-transient properties and applications as photosensors in well-characterized tin telluride (SnTe) single crystal

The current scenario demands new semiconducting materials for the development of fast-reacting sensors, detectors, and special solid-state devices. On the way to finding a solution, alloy engineering has emerged as a vital option for the research community. The present study focuses on the investigation of photo-transient properties and the potential application of a well-characterised Tin Telluride (SnTe) single crystal as a photo-sensor. SnTe has attracted significant attention due to its promising optoelectronic properties and its large suitability for a variety of applications in various fields of material engineering. The present work employs various characterizations/.vm, dmjmof grown single crystals to understand their structural, morphological, and electrical properties. Furthermore, the photo-transient properties of SnTe were investigated by an in-house design setup to study its photo-driven reaction under different illumination conditions. The results reveal the excellent photo-response of the fitted sample, suggesting a fast response time, high sensitivity, and wide spectral reacting ability of the grown crystalline material. Additionally, we explore the feasibility of SnTe as a photosensor by investigating its performance under environmental conditions. The findings indicate that SnTe exhibits remarkable stability and reliability, making it a promising candidate for photo-sensing applications. The insights obtained from this investigation contribute to the understanding of the photo-transient behaviour of SnTe and provide valuable knowledge of optical and photo-responsive parameters for designing efficient photosensors using grown material.

(Invited) CdS/Pd Photocatalytic Bipolar Membrane for Selective Reduction and Oxidation Processes

A bipolar membrane with specific cation exchange and anion exchange properties between the two layers enables design of photocatalytically active membrane which also separate reaction compartments. The key advantage of such a membrane lies in the separation of oxidation and reduction processes while continue to engage in the photodriven reactions. The example of simultaneous oxidation of 4-chlorophenol and the reduction of 4-nitrophenol under visible light irradiation of the BPM-CdS/Pd shows its effectiveness in photocatalytic remediation of chemical contaminants. The CdS-Pd based bipolar membrane to carry out selective reduction and oxidation processes has also allowed us estimate the contribution of sacrificial donor oxidation in H2 production in water photoelectrolysis. The design and photocatalytic properties of this photocatalytic membrane will be discussed.

Emergence of ligand-to-metal charge transfer in homogeneous photocatalysis and photosensitization

Light energy can be harnessed by photosensitizers or photocatalysts so that some chemical reactions can be carried out under milder conditions compared to the traditional heat-driven processes. To facilitate the photo-driven reactions, a large variety of chromophores that are operated via charge transfer excitations have been reported because of their typically longer excited-state lifetimes, which are the key to the downstream photochemical processes. Although both metal-to-ligand charge transfers and ligand-to-metal charge transfers are well-established light absorption pathways; the former has been widely adopted in photocatalysis, whereas the latter has recently taken on greater importance in photosensitization applications. In this article, we review the latest developments on ligand-to-metal charge transfer photosensitization by molecular complexes across the periodic table by focusing homogeneous photocatalysis and the use of photophysical measurements and computational calculations to understand the electronic structures, photochemical processes, structure–activity relationships, and reaction mechanisms. We also present our perspectives on the possible future developments in the field.

Photodriven Dehydrogenative Homocoupling of Benzylic C–H Bonds Forming Strained C–C Bonds

AbstractA photoinduced dehydrogenative homocoupling reaction of alkylarenes is reported. Gaseous hydrogen is evolved as the sole byproduct and neither oxidants nor hydrogen acceptors are required. The present reaction offers an environmentally benign and atom-economical means for forming sterically strained C–C single bonds. It also gives a remarkable example of photodriven reactions overcoming a considerable rise in energy.

Single nanoparticle photoelectrochemistry: What is next?

Semiconductor photoelectrochemistry is a fascinating field that deals with the chemistry and physics of photodriven reactions at solid/liquid interfaces. The interdisciplinary field attracts (electro)chemists, materials scientists, spectroscopists, and theorists to study fundamental and applied problems such as carrier dynamics at illuminated electrode/electrolyte interfaces and solar energy conversion to electricity or chemical fuels. In the pursuit of practical photoelectrochemical energy conversion systems, researchers are exploring inexpensive, solution-processed semiconductor nanomaterials as light absorbers. Harnessing the enormous potential of nanomaterials for energy conversion applications requires a fundamental understanding of charge carrier generation, separation, transport, and interfacial charge transfer at heterogeneous nanoscale interfaces. Our current understanding of these processes is derived mainly from ensemble-average measurements of nanoparticle electrodes that report on the average behavior of trillions of nanoparticles. Ensemble-average measurements conceal how nanoparticle heterogeneity (e.g., differences in particle size, shape, and surface structure) contributes to the overall photoelectrochemical response. This perspective article focuses on the emerging area of single particle photoelectrochemistry, which has opened up an exciting new frontier: direct investigations of photodriven reactions on individual nanomaterials, with the ability to elucidate the role of particle-dependent properties on the photoelectrochemical behavior. Here, we (1) review the basic principles of photoelectrochemical cells, (2) point out the potential advantages and differences between bulk and nanoelectrodes, (3) introduce approaches to single nanoparticle photoelectrochemistry and highlight key findings, and (4) provide our perspective on future research directions.

Photocatalytic Hydrogen Generation by Vesicle-Embedded [FeFe]Hydrogenase Mimics: A Mechanistic Study.

Artificial photosynthesis—the direct photochemical generation of hydrogen from water—is a promising but scientifically challenging future technology. Because nature employs membranes for photodriven reactions, the aim of this work is to elucidate the effect of membranes on artificial photocatalysis. To do so, a combination of electrochemistry, photocatalysis, and time‐resolved spectroscopy on vesicle‐embedded [FeFe]hydrogenase mimics, driven by a ruthenium tris‐2,2′‐bipyridine photosensitizer, is reported. The membrane effects encountered can be summarized as follows: the presence of vesicles steers the reactivity of the [FeFe]‐benzodithiolate catalyst towards disproportionation, instead of protonation, due to membrane characteristics, such as providing a constant local effective pH, and concentrating and organizing species inside the membrane. The maximum turnover number is limited by photodegradation of the resting state in the catalytic cycle. Understanding these fundamental productive and destructive pathways in complex photochemical systems allows progress towards the development of efficient artificial leaves.

Photoreduction of CO2 in an optical-fiber photoreactor: Effects of metals addition and catalyst carrier

Abstract The transformation of CO 2 to hydrocarbons using sunlight is one of best routes to produce renewable energy. Photocatalytic reduction of CO 2 with H 2 O in the gaseous phase is studied by using Cu-Fe/TiO 2 catalyst coated on optical fibers under UVA and UVC irradiation. Catalyst coated optical fibers are assembled in the reactor such that the UV light can enter along the fibers to conduct the photocatalytic reaction on its surface. Methane and ethylene as main products are observed to evolve from this photoreactor. The presence of Fe as a co-dopant in Cu/TiO 2 catalyst is found to synergistically reduce CO 2 with H 2 O to ethylene at the quantum yield and total energy efficiency of 0.024% and 0.016%, respectively. This phenomenon is well explained by an efficient charge transfer mechanism between TiO 2 as a support and Cu as well as Fe as co-dopants. Methane is formed more favorably than ethylene on Cu/TiO 2 . Meanwhile, Fe as a co-dopant on Cu/TiO 2 catalyst is found to depress the methane formation. The photo production of ethylene over catalysts supported on optical fibers presents yields that are one order of magnitude higher than that on the glass plate counterpart. For a given amount of catalyst and light energy, the optical-fiber reactor can utilize light energy efficiently. Many photo-driven reactions will have advantage using such optical-fiber system.