There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Semiconductor photocatalysis has received much attention as a potential solution to the worldwide energy shortage and for counteracting environmental degradation. This article reviews state-of-the-art research activities in the field, focusing on the scientific and technological possibilities offered by photocatalytic materials. We begin with a survey of efforts to explore suitable materials and to optimize their energy band configurations for specific applications. We then examine the design and fabrication of advanced photocatalytic materials in the framework of nanotechnology. Many of the most recent advances in photocatalysis have been realized by selective control of the morphology of nanomaterials or by utilizing the collective properties of nano-assembly systems. Finally, we discuss the current theoretical understanding of key aspects of photocatalytic materials. This review also highlights crucial issues that should be addressed in future research activities.

Nano‐photocatalytic Materials: Possibilities and Challenges

Rising atmospheric levels of carbon dioxide and the depletion of fossil fuel reserves raise serious concerns about the ensuing effects on the global climate and future energy supply. Utilizing the abundant solar energy to convert CO2 into fuels such as methane or methanol could address both problems simultaneously as well as provide a convenient means of energy storage. In this Review, current approaches for the heterogeneous photocatalytic reduction of CO2 on TiO2 and other metal oxide, oxynitride, sulfide, and phosphide semiconductors are presented. Research in this field is focused primarily on the development of novel nanostructured photocatalytic materials and on the investigation of the mechanism of the process, from light absorption through charge separation and transport to CO2 reduction pathways. The measures used to quantify the efficiency of the process are also discussed in detail.

Photocatalytic reduction of CO2 on TiO2 and other semiconductors.

Global warming and climate change concerns have triggered global efforts to reduce the concentration of atmospheric carbon dioxide (CO2). Carbon dioxide capture and storage (CCS) is considered a crucial strategy for meeting CO2 emission reduction targets. In this paper, various aspects of CCS are reviewed and discussed including the state of the art technologies for CO2 capture, separation, transport, storage, leakage, monitoring, and life cycle analysis. The selection of specific CO2 capture technology heavily depends on the type of CO2 generating plant and fuel used. Among those CO2 separation processes, absorption is the most mature and commonly adopted due to its higher efficiency and lower cost. Pipeline is considered to be the most viable solution for large volume of CO2 transport. Among those geological formations for CO2 storage, enhanced oil recovery is mature and has been practiced for many years but its economical viability for anthropogenic sources needs to be demonstrated. There are growing interests in CO2 storage in saline aquifers due to their enormous potential storage capacity and several projects are in the pipeline for demonstration of its viability. There are multiple hurdles to CCS deployment including the absence of a clear business case for CCS investment and the absence of robust economic incentives to support the additional high capital and operating costs of the whole CCS process.

https://www.elsevier.com/__data/assets/pdf_file/0005/96980/Current-status-carbon-capture.pdf

An overview of current status of carbon dioxide capture and storage technologies

A review on g-C3N4-based photocatalysts

The photoelectrochemical performance of Ag coated CeO2 functionalized TiO2 nanotube arrays (AgCeTNT) is investigated here. The sample is prepared via three steps, such as synthesis of TiO2 nanotube by electrochemical anodization, CeO2 functionalization by hydrothermal and Ag coating by Successive Ionic Layer Adsorption and Reaction (SILAR) method. X-ray diffraction (XRD) analysis showed the anatase phase formation after annealing of TiO2 nanotubes. Field Emission Scanning Electron Microscopic (FESEM) images showed the conformal coverage of CeO2 and Ag nanoparticles on the surface of TiO2 nanotubes. Energy Dispersive X-Ray (EDX) analysis confirmed the presence of Ce, Ag, Ti and O in the AgCeTNT sample. Diffuse Reflectance Spectroscopy (DRS) study revealed the enhancement in visible light sensitivity with CeO2 functionalization and further with Ag coating. The photoelectrochemical measurement showed that the AgCeTNT sample exhibits improved photoelectrochemical performance compared to bare TiO2 nanotubes (TNT), CeO2 functionalized TiO2 nanotubes (CeTNT) and Ag coated TiO2 nanotubes (AgTNT) under the illumination of sunlight. This improvement in photoelectrochemical performance happeneddue to the combined effect of favorable band alignment of CeO2 and TiO2 and Surface Plasmon Resonance (SPR) effect of Ag nanoparticles, which lead to superior charge separation, efficient charge transport and enhanced visible light response.

Enhanced photoelectrochemical performance of CeO2 functionalized TiO2 nanotube arrays with Ag coating

Multi scale color coding of fluid flow mixing indicators along integration lines

An analysis on the effect of sensor configuration and geometry of magnetoelastic resonance sensors operating in air

This paper presents long-term production costing as an important decision tool that can be used to assess entry of exogenous players within an otherwise centrally planned, natural monopolistic market. The ex-monopolist emerges as the dominant participant of the restructured market, and continues to play a decisive role in price determination. In doing so, it can apply long-term production costing methods to decide the extent to which entry of independent players should be permissible. On the other hand, the independent entrants can use production costing to weigh their gains in view of the price decided by the ex-monopolist or the policy maker. The specific case of an energy market is examined through a suitably formulated long-term production costing model. A case study shows that transfer of some of the generating units to independent power producers (IPPs) can lead to considerable reduction of production cost and fuel heat consumption associated with utility owned generation. Further, if the choice of generating units to be transferred to IPPs is made with suitable care, then the marginal cost of utility generation can be reduced significantly; thereby lowering the price of electricity.

Introduction of independent players in a centrally planned market: decision support by long-term production costing

Ultrathin g-C3N4 (g-CN) nanosheets are prepared by a two-step thermal exfoliation process in an air atmosphere. X-ray diffraction pattern (XRD) shows that ultrathin g-CN nanosheets have the same crystal structure as that of the bulk g-CN with a slight shift in the peak positions due to the reduction of sheet thickness. Field emission scanning electron microscope (FESEM) images show that the bulk g-CN is converted into ultrathin g-CN nanosheets due to thermal oxidation in an atmosphere, which increases the number of reactive active sites for water splitting. Due to a reduction in sheet thickness of g-CN, quantum confinement happened and thereby increase the bandgap from 2.88 (bulk g-CN) eV to 3.10 eV (ultrathin g-CN). Steady-state photoluminescence (PL) shows a blue shift, and time-resolve photoluminescence (TRPL) shows that the average lifetime of photogenerated charge carrier increases when bulk g-CN is converted into ultrathin g-CN nanosheets. Enhancement in photoelectrochemical performance is observed in ultrathin g-CN nanosheets compared to bulk g-CN due to the increased average lifetime of photogenerated charge carriers and a large number of reactive active sites.

Somnath C. Roy

Papers

Enhanced photoelectrochemical performance of CeO2 functionalized TiO2 nanotube arrays with Ag coating

Multi scale color coding of fluid flow mixing indicators along integration lines

An analysis on the effect of sensor configuration and geometry of magnetoelastic resonance sensors operating in air

Introduction of independent players in a centrally planned market: decision support by long-term production costing

Improved photoelectrochemical performance of ultra thin g-C3N4 nanosheet: A comparative study from bulk to nanoscale