High-Performance Hydroxide Exchange Membrane Fuel Cell Comprising an Atomic Layer-Deposited Silver Cathode

Atomic layer deposition (ALD) is emerging as an efficient tool for the precise manufacture of catalysts, owing to its sophisticated surface tailoring capabilities. To overcome the techno-economic limitations of fuel cell electric vehicles (FCEVs), which are considered suitable alternatives to battery electric vehicles (BEVs), the development of cost-efficient high-performance catalysts is essential. In this study, we successfully fabricated a Pt-free cathode for a hydroxide exchange membrane fuel cell (HEMFC) with excellent oxygen reduction activity under extremely low loading of Ag electrocatalysts using ALD. Microstructural analysis confirmed that the surface modification by ALD-Ag nanoparticles exhibited excellent step coverage characteristics on porous carbon nanotubes (CNTs). An HEMFC comprising a CNT cathode surface-decorated with ALD-Ag nanoparticles delivered a high peak power density of 2154 mW mgAg-1 in an alkaline environment at 65 °C. This study demonstrates the applicability of ALD for the manufacture of highly active low-cost electrocatalysts for high-performance HEMFCs.

Possible Charge-Transfer-Induced Conductivity Enhancement in TiO2 Microtubes Decorated with Perovskite CsPbBr3 Nanocrystals

Halide perovskite CsPbBr₃ quantum dots (QDs) were synthesized via supersaturated recrystallization process and deposited on the surface of TiO₂ microtubes forming local nano-heterostructures. Structural, morphological, and optical characterizations confirm the formation of heterostructures comprised of TiO₂ microtube decorated with green-emitting CsPbBr₃ nanocrystals. Optical characterizations reveal the presence of two band gap energies corresponding to CsPbBr₃ (2.34 eV) and rutile-TiO₂ (2.97 eV). Time-resolved photoluminescence decays indicate different charge dynamics when comparing both samples, revealing the interaction of CsPbBr₃ QDs with the microtube surface and thus confirming the formation of local nano-heterostructures. The voltage-current measurements in the dark show an abrupt decrease in the electrical resistivity of the CsPbBr₃/TiO₂ heterostructure reaching almost 95% when compared with the pristine TiO₂ microtube. This significant increase in the electrical conductivity is associated with charge transfer from perovskite nanocrystals into the semiconductor microtube, which can be used to fine tune its electronic properties. Besides controlling the electrical conductivity, decoration with semiconducting nanocrystals makes the hollow heterostructure photoluminescent, which can be classified as a multifunctionalization in a single device.

TiO2/porous adsorbents: Recent advances and novel applications

This article reviews two interrelated areas of research: the first is the use of TiO₂-supported adsorbent materials as enhanced heterogeneous photocatalysts and their application to various reactions for organic pollutant removal from air and water; the second is the combination of adsorbent materials with TiO₂ photocatalysts which aims to efficiently regenerate adsorbent materials using illumination. By reviewing both areas of research, the following topics are covered; (i) photocatalytic activation of TiO_2; (ii) related properties of photocatalytic TiO_2; (iii) shortcomings of photocatalytic processes; (iv) preparation methods of composite TiO₂/adsorbent materials and their photocatalytic performance; (v) properties of common adsorbents and their applications for pollutant removal from air and water; (vi) adsorbent regeneration methods and their economic and operational issues; (vii) conclusions and future outlooks. This topic has not been previously reviewed to such an extent, and considerable knowledge can be gained from assembling the large number of studies on adsorption-photocatalysis combinations. As such, this review provides guidance for researchers working in the fields of environmental and chemical engineering focussing on organic pollutant removal and the engineering of new high performance photocatalytic TiO₂-supported porous adsorbent materials.

Continuous synthesis of hedgehog-like Ag–ZnO nanoparticles in a two-stage microfluidic system

Hedgehog-like Ag–ZnO nanoparticles were successfully prepared in a continuous microfluidic system and showed a superior photocatalytic activity in the degradation of methyl orange.

Quantum-Spillover-Enhanced Surface-Plasmonic Absorption at the Interface of Silver and High-Index Dielectrics

We demonstrate an unexpectedly strong surface-plasmonic absorption at the interface of silver and high-index dielectrics based on electron and photon spectroscopy. The measured bandwidth and intensity of absorption deviate significantly from the classical theory. Our density-functional calculation well predicts the occurrence of this phenomenon. It reveals that due to the low metal-to-dielectric work function at such interfaces, conduction electrons can display a drastic quantum spillover, causing the interfacial electron-hole pair production to dominate the decay of surface plasmons. This finding can be of fundamental importance in understanding and designing quantum nanoplasmonic devices that utilize noble metals and high-index dielectrics.

Design and functionalization of photocatalytic systems within mesoporous silica

In the past decades, various photocatalysts such as TiO2, transition-metal-oxide moieties within cavities and frameworks, or metal complexes have attracted considerable attention in light-excited catalytic processes. Owing to high surface areas, transparency to UV and visible light as well as easily modified surfaces, mesoporous silica-based materials have been widely used as excellent hosts for designing efficient photocatalytic systems under the background of environmental remediation and solar-energy utilization. This Minireview mainly focuses on the surface-chemistry engineering of TiO2/mesoporous silica photocatalytic systems and fabrication of binary oxides and nanocatalysts in mesoporous single-site-photocatalyst frameworks. Recently, metallic nanostructures with localized surface plasmon resonance (LSPR) have been widely studied in catalytic applications harvesting light irradiation. Accordingly, silver and gold nanostructures confined in mesoporous silica and their corresponding catalytic activity enhanced by the LSPR effect will be introduced. In addition, the integration of metal complexes within mesoporous silica materials for the construction of functional inorganic-organic supramolecular photocatalysts will be briefly described.

Silver-modified mesoporous TiO2 photocatalyst for water purification

Mesoporous anatase (TiO(2)) was modified with silver (Ag) nanoparticles using a photoreduction method. Performance of the resulting TiO(2)-Ag nanocomposites for water purification was evaluated using degradation of Rhodamine B (RhB) and disinfection of Escherichia coli (E. coli) under ultraviolet (UV) irradiation. The composites with different Ag loadings were characterized using physical adsorption of nitrogen, X-ray diffraction, X-ray photoelectron spectroscopy and UV-Visible diffuse reflectance spectroscopic techniques. The results showed that metallic Ag nanoparticles were firmly immobilized on the TiO(2) surface, which improved electron-hole separation by forming the Schottky barrier at the TiO(2)-Ag interface. Photocatalytic degradation of RhB and inactivation of E. coli effectively occurred in an analogical trend. The deposited Ag slightly decreased adsorption of target pollutants, but greatly increased adsorption of molecular oxygen with the latter enhancing production of reactive oxygen species (ROSs) with concomitant increase in contaminant photodegradation. The optimal Ag loadings for RhB degradation and E. coli disinfection were 0.25 wt% and 2.0 wt%, respectively. The composite photocatalysts were stable and could be used repeatedly under UV irradiation.