Promoting Photon-to-Chemical Conversion through a Dielectric Antenna-Hybrid Bilayered Reactor Configuration

The application of scattered light via an antenna-reactor configuration is promising for converting thermocatalysts into photocatalysts. However, the efficiency of dielectric antennas in photon-to-chemical conversion remains suboptimal. Herein, we present an effective approach to promote light utilization efficiency by designing dielectric antenna-hybrid bilayered reactors. Experimental studies and finite-difference time-domain simulations demonstrate that the engineered SiO2-carbon/metal dielectric antenna-hybrid bilayered reactors exhibit a synergy of absorption superposition and electric field confinement between carbon and metals, leading to the improved absorption of scattered light, upgraded charge carriers density, and ultimately promoted photoactivity in hydrogenating chlorobenzene with an average benzene formation rate of 18 258 μmol g-1 h-1, outperforming the reported results. Notably, the carbon interlayer proves to be more effective than the commonly explored dielectric TiO2 interlayer in boosting the benzene formation rate by over 3 times. This research paves the way for promoting near-field scattered photon-to-chemical conversion through a dielectric antenna-hybrid reactor configuration.

Developing Catalysts Integrated in Gas-Diffusion Electrodes for CO2 Electrolyzers

ConspectusAs the demand for a carbon-neutral society grows rapidly, research on CO2 electrolysis has become very active. Many catalysts are reported for converting CO2 into value-added products by electrochemical reactions, which have to perform at high Faradaic and energy efficiency to become commercially viable. Various types of CO2 electrolyzers have been used in this effort, such as the H-cell, flow cell, and zero-gap membrane-electrode assembly (MEA) cell. H-cell studies are conducted with electrodes immersed in CO2-saturated electrolyte and have been used to elucidate reaction pathways and kinetic parameters of electrochemical CO2 reduction on many types of catalytic surfaces. From a transport phenomenological perspective, the low solubility and diffusion of CO2 to the electrode surface severely limit the maximum attainable current density, and this metric has been shown to have significant influence on the product spectrum. Flow and MEA cells provide a solution in the form of gas-diffusion electrodes (GDEs) that enable gaseous CO2 to closely reach the catalyst layer and yield record-high current densities. Because GDEs involve a complicated interface consisting of the catalyst surface, gaseous CO2, polymer overlayers, and liquid electrolyte, catalysts with high intrinsic activity might not show high performance in these GDE-based electrolyzers. Catalysts showing low overpotentials at low current densities may suffer from poor electron conductivity and mass transfer limitations at high current densities. Furthermore, the stability of the GDE-based catalysts is often compromised as CO2 electrolysis is pursued with high activity, most notoriously by electrolyte flooding.In this Account, we introduce recent examples where the electrocatalysts were integrated in GDEs, achieving high production rates. The performance of such systems is contingent on both GDE and cell design, and various parameters that affect the cell performance are discussed. Gaseous products, such as carbon monoxide, methane, and ethylene, and liquid products, such as formate and ethanol, have been mainly reported with high partial current density using the flow or MEA cells. Different strategies to this end are described, such as controlling microenvironments by the use of polymers mixed within the catalyst layer or the functionalization of catalyst surfaces with ligands to increase local concentrations of intermediates. Unique CO2 electrolyzer designs are also treated, including the incorporation of light-responsive plasmonic catalysts in the GDE, and combining the electrolyzer with a fermenter utilizing a microbial biocatalyst to synthesize complex multicarbon products. Basic conditions which the catalyst should satisfy to be adapted in the GDEs are listed, and our perspective is provided.

Engineering the Metal/Dielectric Interface to Unlock the Potential of Scattered Light for Boosted Photoredox Catalysis

The recycling of scattered light by metals has been emerging as a promising light-manipulation-capture strategy, but how to bring its potential into better play remains to be explored. Herein, we present that constructing dual metal/high-refractive-index dielectric interfaces within the SiO2 core@TiO2 shell-Pd satellite@TiO2 shell effectively strengthens both the scattering efficiency of the dielectric SiO2 support and electric field confinement. Consequently, the absorption of Pd toward near-field scattered light and the interfacial charge carrier separation are both enhanced. The synergy of these effects leads to boosted photoactivity toward the aerobic oxidation of cyclohexanol to cyclohexanone and the anaerobic reduction of proton for hydrogen evolution under visible-light irradiation as compared to the counterparts with a single metal/dielectric interface and dual metal/dielectric interfaces consisting of low-refractive-index dielectric component. Notably, the similar enhancements in both optical absorption and photoactivity can be achieved through the present dual metal/high-refractive-index dielectric interfaces engineering strategy for other metals, such as Pt nanoparticles. This work presents an instructive avenue to upgrade the optical response of metals and thus the photocatalytic performance by engineering metal/dielectric interfaces.

Nanobiotechnological approaches in anticoagulant therapy: The role of bioengineered silver and gold nanomaterials

Nanotechnology is a novel area that has exhibited various remarkable applications, mostly in medicine and industry, due to the unique properties coming with the nanoscale size. One of the notable medical uses of nanomaterials (NMs) that attracted enormous attention recently is their significant anticoagulant activity, preventing or reducing coagulation of blood, decreasing the risk of strokes, heart attacks, and other serious conditions. Despite successful in vitro experiments, in vivo analyses are yet to be confirmed and further research is required to fully prove the safety and efficacy of nanoparticles (NPs) and to introduce them as valid alternatives to conventional ineffective anticoagulants with various shortcomings and side-effects. NMs can be synthesized through two main routes, i.e., the bottom-up route as a more preferable method, and the top-down route. In numerous studies, biological fabrication of NPs, especially metal NPs, is highly suggested given its eco-friendly approach, in which different resources can be employed such as plants, fungi, bacteria, and algae. This review discusses the green synthesis and characterization of silver nanoparticles (AgNPs) and gold nanoparticles (AuNPs) as two of the most useful metal NPs, and also their alloys in different studies focussing on their anticoagulant potential. Challenges and alternative approaches to the use of these NPs as anticoagulants have also been highlighted.

Exploiting the LSPR effect for an enhanced photocatalytic hydrogen evolution reaction

Incorporation of plasmonic metals is one of the most widely adopted strategies for improving the photocatalytic hydrogen evolution reaction (HER) activity of semiconductor photocatalysts. This article summarizes recent advances in the development of plasmonic metal-semiconductor photocatalysts and four localized surface plasmon resonance (LSPR) driven mechanisms by which plasmonic metal nanoparticles can contribute to enhancement of HER activity. In addition, principles for maximizing the contribution of these LSPR driven mechanisms are highlighted to provide insights for future design of plasmonic metal-semiconductor photocatalysts with enhanced HER activity.

Highly Durable Heterogeneous Atomic Catalysts

ConspectusSingle-atom catalysts (SACs), in which surface metal atoms are isolated on the surface of a support, have received a tremendous amount of attention recently because this structure would utilize precious metals fully, without occluding atoms inside nanoparticles, and enable unique surface reactions which typical nanoparticle catalysts cannot induce. Various synthesis methods and characterization techniques have been reported that yield enhanced activity and selectivity. The single-atom structures were realized on various supports such as metal oxide/carbide/nitride, porous materials derived from zeolite or metal-organic frameworks, and carbon-based materials. Additionally, when the metal atoms are isolated on other metal nanoparticles, this material is denoted as a single-atom alloy (SAA). The single-atom structure, however, cannot catalyze the surface reaction that necessitates ensemble sites, where several metal atoms are located nearby. Very recently, ensemble catalysts, in which all of the metal atoms are exposed at the surface with neighboring metal atoms, have been reported, overcoming the limitation of single-atom catalysts. We call all of these materials (SACs, SAAs, and ensemble catalyst) heterogeneous atomic catalysts, indicating that the surface metal atomic structure is intentionally controlled. To use these atomic catalysts for practical applications, high durability should be guaranteed, which has received relatively less attention.In this Account, we discuss recent examples of heterogeneous atomic catalysts with high durability. Structural stability, indicating whether the surface atomic structure is thermodynamically stable, should be carefully considered. Typically, metal atoms are immobilized on a highly defective support, stabilizing both the metal atom and the support. The surface metal atoms might become destabilized upon the adsorption of chemical intermediates. This transient behavior should be carefully monitored; density functional theory (DFT) calculations are particularly useful in estimating this stability. Aside from structural stability, the catalyst performance can be degraded significantly by poisoning with impurities. If the single-atom sites are susceptible to impurities with stronger adsorption, the surface reaction would not occur efficiently, leading to a decrease in activity without structure degradation. A long-term durability test should be performed for target reactions. Heterogeneous atomic catalysts have been used for various electrochemical, photocatalytic, and thermal reactions. Although electricity, light, and heat are just different forms of energy, the specific conditions which the catalyst should satisfy are different. Whereas precious metal atoms are mostly used as surface-active sites, the properties of the support are different depending on the type of reaction. For example, the support should have high conductivity for electrochemical reactions, it should be able to absorb light for photocatalytic reactions, and it should be durable at high temperature in the presence of steam for thermal reactions. Highly durable heterogeneous atomic catalysts are certainly possible with a great potential for practical applications. These new catalysts can accelerate the current paradigm shift toward more sustainable chemical production.

Visible and NIR Light Assistance of the N2 Reduction to NH3 Catalyzed by Cs-promoted Ru Nanoparticles Supported on Strontium Titanate

NH₃ production accounts for more than 1% of the total CO₂ emissions and is considered one of the most energy-intensive industrial processes currently (T > 400 °C and P > 80 bars). The development of atmospheric-pressure N₂ fixation to NH₃ under mild conditions is attracting much attention, especially using additional renewable energy sources. Herein, efficient photothermal NH₃ evolution in continuous flow upon visible and NIR light irradiation at near 1 Sun power using Cs-decorated strontium titanate-supported Ru nanoparticles is reported. Notably, for the optimal photocatalytic composition, a constant NH₃ rate near 3500 μmol_NH3 g_catalyst^–1 h^–1 was achieved for 120 h reactions, being among the highest values reported at atmospheric pressure under 1 Sun irradiation.

Non-Noble Plasmonic Metal-Based Photocatalysts

Solar-to-chemical energy conversion via heterogeneous photocatalysis is one of the sustainable approaches to tackle the growing environmental and energy challenges. Among various promising photocatalytic materials, plasmonic-driven photocatalysts feature prominent solar-driven surface plasmon resonance (SPR). Non-noble plasmonic metals (NNPMs)-based photocatalysts have been identified as a unique alternative to noble metal-based ones due to their advantages like earth-abundance, cost-effectiveness, and large-scale application capability. This review comprehensively summarizes the most recent advances in the synthesis, characterization, and properties of NNPMs-based photocatalysts. After introducing the fundamental principles of SPR, the attributes and functionalities of NNPMs in governing surface/interfacial photocatalytic processes are presented. Next, the utilization of NNPMs-based photocatalytic materials for the removal of pollutants, water splitting, CO₂ reduction, and organic transformations is discussed. The review concludes with current challenges and perspectives in advancing the NNPMs-based photocatalysts, which are timely and important to plasmon-based photocatalysis, a truly interdisciplinary field across materials science, chemistry, and physics.

Laser-Promoted Immobilization of Ag Nanoparticles: Effect of Surface Morphology of Poly(ethylene terephthalate)

In the last two decades, the importance of nanomaterials in modern technologies has been unquestionable. Metal nanoparticles are frequently used in many areas of science and technology, delivering unprecedented improvements to properties of the conventional materials. This work introduces an effective tool for preparing a highly enriched poly (ethylene terephthalate) (PET) surface with silver nanoparticles, firmly immobilized in the same surface area on polymer. We showed that besides pristine polymer, this approach may be successfully applied also on laser pre-treated PET with laser-induced periodic surface structures. At the same time, its final nanostructure may be effectively controlled by laser fluence applied during the immobilization process.

Photo-assisted electrochemical CO2 reduction using a translucent thin film electrode

Herein, we introduce a new concept of photo-assisted electrochemical CO₂ reduction through a translucent thin film electrode. The light-compatible thin film electrode directly exposes Au nanoparticle-loaded Ag nanowires to gaseous CO₂, obtaining a CO production rate of 0.7 mmol cm^-2 h^-1 with a photocurrent density of 6.05 mA cm^-2 at -1.1 V_RHE.