Selective production of hydrogen peroxide and oxidation of hydrogen sulfide in an unbiased solar photoelectrochemical cell

A solar-to-chemical conversion process is demonstrated using a photoelectrochemical cell without external bias for selective oxidation of hydrogen sulfide (H2S) to produce hydrogen peroxide (H2O2) and sulfur (S). The process integrates two redox couples anthraquinone/anthrahydroquinone and I−/I3−, and conceptually illustrates the remediation of a waste product for producing valuable chemicals

Nanohybrid materials of titania nanosheets and plasmonic gold nanoparticles for effective hydrogen evolution

A new type of nanocomposites containing titania and gold were prepared via the coupling between exfoliated TiO nanosheets and surfactant-capped Au nanoparticles, followed by flocculation and calcination. After hybridization with TiO nanosheets, octahedral Au nanoparticles were embedded intimately into the matrix of titania, leading to a broad absorption peak assigned to surface plasmon resonance (SPR) effect in the visible region. The obtained nanocomposite exhibited remarkably improved photocatalytic hydrogen evolution performance compared to naked titania and conventional titania with photodeposited Au co-catalyst, due to the special SPR effect of the relatively large octahedral Au nanoparticles. Through control experiments, we demonstrated that the octahedral Au nanoparticles mainly functioned as local light intensifier and photon scattering agent

Processable graphene oxide-embedded titanate nanofiber membranes with improved filtration performance

Graphene oxide (GO)-embedded titanate nanofiber (TNF) membranes with improved filtration performance are prepared successfully by a two-step method including electrostatic assembly of GO and TNFs into hybrids and subsequent processing of them into membranes by vacuum filtration. The embedded contents of GO sheets in films and thickness of as-assembled films can be adjusted facilely, endowing such composite films with good processability. Owing to the skilful introduction of GO sheets, the pore and/or channel structures in these hybrid membranes are modified. By treating different dye solutions (Direct Yellow and Direct Red), the filtration properties of these membranes show that the introduction of certain amount of GO sheets efficiently improve the separation performance of the membranes. Interestingly, these GO-embedded TNF membranes also display superior selective separation performance on filtrating the mixture solutions of such two dyes, making these hierarchical membranes more flexible and versatile in water treatment areas

Flowing water enabled piezoelectric potential of flexible composite film for enhanced photocatalytic performance

Fast charge transfer and low recombination rate are two vital requirements to achieve high photocatalytic activity. In this work, we report the conversion of flowing water energy to piezoelectric potential on a new type of flexible composite film PVDF-NaBiTiO-BiOClBr (PV-N-B) containing PVDF-NaBiTiO (PV-N) substrate and BiOClBr, which significantly boosts the charge transfer of the photocatalytic composite film, resulting in improved photocatalytic capability by 2.33 times. The role of piezoelectric potential in photocatalysis process has been discussed in detail and the results reveal that higher potential output is more beneficial for photocatalytic performance enhancement. Moreover, the photocatalytic degradation intermediates of tetracycline (TC) over PV-N-B were detected by liquid chromatography-mass spectrometer and the possible photodegradation pathway of TC has been reasonably proposed. It is verified that superoxide radicals are the main active species for PV-N-B to degrade TC. The durability experiments demonstrate the good stability of flexible composite film PV-N-B. In a wider perspective, this work provides an efficient flexible composite film, with great capability in converting flowing water energy into piezoelectric potential and improving photocatalytic activity, to bring the environmental pollution under control

Ion-exchangeable semiconductor materials for visible light-induced photocatalysis

The use of semiconductor materials for solar fuel production and environmental remediation has attracted increasing attention in the past decades due to their potential to address important energy and environmental problems. Ion-exchangeable semiconductor materials represent one family of promising materials due to their unique crystal structures and structure-related photocatalytic activity. However, most of the ion-exchangeable semiconductor materials can only absorb UV light due to their wide band-gap. To efficiently utilize solar energy, it is indispensable to develop visible light-responsive semiconductor materials which can efficiently absorb solar electromagnetic radiation reaching the Earth's surface. In this review article, we summarize the recent advances on ion-exchangeable semiconductor materials as visible light-responsive photocatalysts with particular focus on the band-gap engineering strategies and their photocatalytic applications

Nanomaterials for water splitting

This chapter starts with a brief introduction to the knowledge of water splitting on semiconductor nanocatalysts. Then it overviews the semiconductor nanocatalysts according to their light absorption property and element compositions. In the real photocatalytic water-splitting reactions, different aspects affecting the reaction dynamics such as stability of photocatalysts, overpotential, reaction media, and lifetime of photogenerated charges should be considered. To develop an “omnipotent” semiconductor photocatalyst, efforts in the following two aspects should be considered. First, the fundamental issue affecting the photocatalytic water-splitting process needs to be clearly illustrated at a microcosmic level. This could be realized with the development of advanced characterization techniques such as time-revolved infrared and fluorescence spectroscopy. Second, the novel band-gap engineering strategy and synthesis methods should be developed to fine-tune the crystal structure, electronic structure, surface state, and morphology of photocatalysts

On the engineering part of solar hydrogen production from water splitting: Photoreactor design

Water splitting under sunlight illumination in the presence of semiconductor photocatalyst is a very promising way to produce clean hydrogen fuel. Solar hydrogen can be obtained in two routes: photoelectrochemical (PEC) water splitting based on immobilized photocatalysts in thin films and photocatalytic (photochemical) water splitting based on powder photocatalysts in slurry system. Over the past several decades, tremendous research work has been devoted to exploring new semiconductor materials suitable for PEC and photochemical systems and understanding the underlying mechanism of the water splitting process. However, much less attention has been paid to the design of photocatalytic reaction systems or reactors, which is indeed critically important for the overall solar energy conversion performance. This paper summarizes the basic working mechanisms of both PEC and photochemical systems, and gives an overview of a variety of photoreactor design and development

Boosting the efficiency of quantum dot sensitized solar cells up to 7.11% through simultaneous engineering of photocathode and photoanode

We demonstrate a new strategy of boosting the efficiency of quantum dot sensitized solar cells (QDSSCs) by engineering the photocathode and photoanode simultaneously. Nanostructured photocathodes based on non-stoichiometric Cu2-xSe electrocatalysts were developed via a simple and scalable approach for CdS/CdSe QDs co-sensitized solar cells. Compared to Cu2S CE, remarkably improved photovoltaic performance was achieved for QDSSCs with Cu2-xSe CEs. The superior catalytic activity and electrical conductivity of Cu2-xSe CEs were verified by the electrochemical impedance spectra and Tafel-polarization measurements. To maximize the efficiency enhancement, the photoanodes were optimized by introducing a pillared porous titania composite as the scattering layers for further light harvesting and charge transfer improvement concurrently. The combination of effective Cu2-xSe electrocatalysts and pillared titania scattering layers contributed to one of the best reported efficiencies of 7.11% for CdS/CdSe QDs co-sensitized solar cells

Interconnected graphene hollow shells for high-performance capacitive deionization

Electrochemical capacitive deionization (CDI) is a promising technology for distributed and energy-efficient water desalination. The development of high-performance capacitive electrodes is critical for enhancing CDI properties and scaling up its applications. Herein, a three-dimensional graphene porous architecture with high CDI performance is successfully constructed by assembling intentionally designed incomplete graphene-based spherical hollow shells. Small graphene oxide (GO) sheets are purposely adopted to prepare sphere shells by wrapping the surface of polystyrene sphere templates. Because the small-sized GO sheets cannot enwrap the spherical templates seamlessly, a unique graphene hollow shell structure with integrally interconnected feature forms upon removal of the templates. Compared to control samples with typical isolated pore structure (3DGA-C) prepared with commonly used large-sized GO sheets, such open and interconnected porous architectures (3DGA-OP) greatly increase their accessibility of specific surface area and pore volume, enabling superior electrochemical performance. The optimized CDI capacities of 3DGA-OP electrodes reach up to 14.4 mg.g(-1) in NaCl aqueous of 500 mg.L-1 at 1.2 V, which is about 2 times the 3DGA-C ones (6.7 mg.g(-1)) and exceeds the CDI values of most reported pure graphene electrodes under the same experimental conditions. This strategy of improving the open interconnectivity between pores illuminates new avenues for developing high performance CDI porous electrodes assembled from two-dimensional materials

A new type of carbon nitride-based polymer composite for enhanced photocatalytic hydrogen production

A new type of graphitic C3N4-based composite photocatalysts was designed and prepared by co-loading PEDOT as a hole transport pathway and Pt as an electron trap on C3N4. The as-prepared C3N4-PEDOT-Pt composites showed drastically enhanced activity for visible light-driven photocatalytic H2 production compared to those of C3N4-PEDOT and C 3N4-Pt, possibly due to the spatial separation of the reduction and oxidation reaction sites. This journal i