Summary

Semiconductor photocatalysts play a crucial role when it comes to environmental issues such as global warming, pollutant degradation, fuel shortage, and energy crisis In this paper, three nanostructured compound (3-, 4-, and 5-component) semiconductor materials were synthesized through a facile one-pot hydrothermal method, and were applied as alloy photocatalysts to generate hydrogen fuel via a water photo-splitting process Nitrogen adsorption–desorption isotherms revealed that the synthesized materials were all mesoporous and the highest surface area was witnessed for Ag-doped quinary photocatalyst, viz Cd01Zn087Sn001Ag001S (CZTSS) This heterogeneous photocatalyst exhibited a maximum performance in evolving hydrogen gas The superiority of CZTSS was justified in terms of its greater surface area, higher conduction band and its silver plasmon resonance, enhancing the light absorption at long wavelengths Field emission scanning electron microscopy revealed a spectacular nanostructure for this photocatalyst that was comprised of nanoparticles, platelets, and microspheres attached together Energy dispersive X-ray (EDX) analyses of the CZTSS also proved the synthesis of the quinary photocatalyst, having different compositions in distinct zones Copyright © 2014 John Wiley & Sons, Ltd

A highly efficient nanostructured quinary photocatalyst for hydrogen production

A redox electrolyte is a crucial part of dye-sensitized solar cells (DSSCs), which plays a significant role in the photovoltage and photocurrent of the DSSCs through efficient dye regeneration and minimization of charge recombination. An I–/I3– redox shuttle has been mostly utilized, but it limits the open-circuit voltage (Voc) to 0.7–0.8 V. To improve the Voc value, an alternative redox shuttle with more positive redox potential is required. Thus, by utilizing cobalt complexes with polypyridyl ligands, a significant power conversion efficiency (PCE) of above 14% with a high Voc of up to 1 V under 1-sun illumination was achieved. Recently, the Voc of a DSSC has exceeded 1 V with a PCE of around 15% by using Cu-complex-based redox shuttles. The PCE of over 34% in DSSCs under ambient light by using these Cu-complex-based redox shuttles also proves the potential for the commercialization of DSSCs in indoor applications. However, most of the developed highly efficient porphyrin and organic dyes cannot be used for the Cu-complex-based redox shuttles due to their higher positive redox potentials. Therefore, the replacement of suitable ligands in Cu complexes or an alternative redox shuttle with a redox potential of 0.45–0.65 V has been required to utilize the highly efficient porphyrin and organic dyes. As a consequence, for the first time, the proposed strategy for a PCE enhancement of over 16% in DSSCs with a suitable redox shuttle is made by finding a superior counter electrode to enhance the fill factor and a suitable near-infrared (NIR)-absorbing dye for cosensitization with the existing dyes to further broaden the light absorption and enhance the short-circuit current density (Jsc) value. This review comprehensively analyzes the redox shuttles and redox-shuttle-based liquid electrolytes for DSSCs and gives recent progress and perspectives.

https://pubs.acs.org/doi/pdf/10.1021/acsomega.2c06843

Redox Shuttle-Based Electrolytes for Dye-Sensitized Solar Cells: Comprehensive Guidance, Recent Progress, and Future Perspective

We firstly, in this review, introduce the optical properties of plasmonic metals, and then focus on introducing the unique optical properties of the noble metal–metal-oxide hybrid system by revealing the physical mechanism of plasmon–exciton interaction, which was confirmed by theoretical calculations and experimental investigations. With this noble metal–metal-oxide hybrid system, plasmonic nanostructure–semiconductor exciton coupling interactions for interface catalysis has been analyzed in detail. This review can provide a deeper understanding of the physical mechanism of exciton–plasmon interactions in surface catalysis reactions.

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Nanoplasmon–Semiconductor Hybrid for Interface Catalysis

The structure and quality of the TiO2 is crucial for achieving high efficiency in dye-sensitized solar cells (DSCs). In this work we have studied the effect of annealing temperature, TiCl4 concentration/ treatment time and the number of the TiO2 layers on the performance of a DSC device. It is found that increasing the annealing temperature and treatment time with application of diluted TiCl4 increased the efficiency. These items along with including a bi-layer semiconductor led to a 30% performance increase in comparison to the original solar cell just by considering the best concentration and time product for TiCl4 treatment step. The enhancement in the performance is likely due to high porosity of the semiconductor layer. Also, the lessened TiCl4 concentration decreases the harmful effects of the harsh solution but still allows for band edge improvement. Lastly, the bi-layer consisted of transparent and opaque TiO2 paste. The first consist of 15-20nm particles and the latter comprises of ~100 nm particles. Each contributes to enhancement, as the dye and sunlight have greater absorption and scattering capabilities. Currently in progress is the synthesis and fabrication of new dyes, for compatibility efforts with the semiconductor.

Study the effect of TiO 2 annealing and TiCl 4 treatment on the performance of dye-sensitized solar cells

The one side selective synthesis of quinoline carboxylic acid oxime complex was carried out successfully. The as-prepared quinoline carboxylic acid oxime complex was complexed with nickel (II) salts to form nickel (II) oxime complex. These complexes were further adsorbed onto ZnO  films containing ZnO nanoparticles of various sizes. ZnO films containing a diverse proportion of ZnO nanoparticles were investigated to enhance the photovoltaic efficiency of the dye-sensitized solar cell. The as-synthesized complex was characterized by scanning electron microscopy (SEM), Ultra violet visible spectroscopy (UV-vis), Fourier Transform Infrared Spectroscopy (FT-IR) spectroscopy, 1Hydrogen Nuclear magnetic resonance spectroscopy (1HNMR), Liquid chromatography coupled with mass spectrometry (LC-MR), Brunauer–Emmett–Teller (BET), and Attenuated total reflection Infra-red spectroscopy (ATR-IR). The combination of large and small ZnO nanoparticles has significantly improves the photovoltaic efficiency. The optimum mixing ratio for the best performance (0.127%) of a dye-sensitized solar cell is achieved by mixing the small: large ZnO particles in a ratio 60:40. The increased efficiency is due to the harvesting of light caused by scattering effect from larger sized ZnO particles. The ZnO layer consisting of smaller particles which are very next to the ZnO bigger particles makes a good electronic contact between film electrode and the Indium-doped tin oxide glass substrate resulting in the increases in the dye molecules adsorption. The over-layered, large-sized ZnO particles enhance the light-harvesting by light scattering effect. Compared to the other mixtures of ZnO films, there is a decrease in the photovoltaic performance of the solar cell when ZnO particles (small and large in a ratio 1:1) were adsorbed onto the Ni (II) oxime complex, which are caused due to the decrease in the surface area and dye aggregation.

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Influence of Ni (II) oxime complex coupled with the combination of diverse sized ZnO nanoparticles on Photovoltaic Performance

cis-X~Bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) complexes (X = C1-, Br, I-, CN-, and SCN-) were prepared and characterized with respct to their absorption, luminescence, and redox behavior. They act as efficient charge-transfer sensitizers for nanocrystalline Ti02 films (thickness 8-1 2 pm) of very high internal surface area (roughness factor ca. lOOO), prepared by sintering of 15-30-nm colloidal titania particles on a conducting glass support. The performance of cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) (1) was found to be outstanding and is unmatched by any other known sensitizer. Nanocrystalline Ti02 films coated with a monolayer of 1 harvest visible light very efficiently, their absorption threshold being around 800 nm. Conversion of incident photons into electric current is nearly quantitative over a large spectral range. These films were incorporated in a thin-layer regenerative solar cell equipped with a light-reflecting counter electrode. Short-circuit photocurrents exceeding 17 mA/cmZ were obtained in simulated AM 1.5 sunlight using lithium iodide/triiodide in acetonitrile or acetonitrile/ 3-methyl-2-oxazolidinone mixtures as redox electrolyte. The open-circuit photovoltage was 0.38 V and increased to 0.72 V by treating the dye-covered film with 4-terr-butylpyridine. A solar-to-electric energy conversion efficiency of 10% was attained with this system. The effect of temperature on the power output and long-term stability of the dye was also investigated. For the first time, a device based on a simple molecular light absorber attains a conversion efficiency commensurate with that of conventional silicon-based photovoltaic cells. a broad spectral range in the~isible.~ A subsequent time-resolved luminescence study by Eichberger and Willig3m showed this effect to be due to ultrafast (7 < 7 ps) electron injection from the excited state of the complex into the conduction band of the oxide occurring with a quantum yield near 100%. These important observations warrant further studies of the behavior of the relatively unexplored class of bis(2,2'-bipyridyl)ruthenium(II)- type redox sensitizers. Apart from their chemical stability and ease of interfacial charge exchange with semiconducting solids, the attractive feature of these complexes is their large visible light harvesting capacity which is superior to that of the widely studied tris(bipyridy1) Ru(I1) analogues, making them a judicious choice for solar energy conversion devices.

E. Miiller

Papers

Charge-Transfer Sensitizers (X = C1-, Br-, I-, CN-, and SCN-) on Nanocrystalline Ti02 Electrodes