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Photocatalytic gas phase reactions represent a less explored yet promising direction within the highly active research area of photocatalysis. While photocatalytic liquid phase reactions are typically performed in water, photocatalytic gas phase reactions focus on gaseous and vaporized compounds. With this change in reaction environment, it is possible to address completely new questions and topics. Examples lie in the field of solar fuels, air pollution, global warming, and green chemistry. For this review, we selected five photocatalytic gas phase reactions, namely the reduction of CO2, water splitting, the oxidation of volatile organic compounds, the degradation of nitrogen oxides, and the synthesis of ammonia, which we discuss in the context of why they are important from a scientific, technological, and also societal point of view. We present the chemical mechanisms behind these photocatalytic processes and propose ideas and strategies for how these processes can be made more efficient. Our literature survey results in a list of 11 points regarding how the selectivity and yield of photocatalytic gas phase reactions can be increased by optimizing the composition of the photocatalysts, their surface chemistry, and experimental parameters such as temperature, gas flow, and gas composition.

Chemical design criteria for materials for bioelectronics applications using a series of copolymer derivatives based on poly(3-hexylthiophene) are established. Directed chemical design via side-chain functionalization with polar groups allows manipulation of ion transport and ion-to-electron transduction. Insights gained will permit increased use of the plethora of materials employed in the organic electronics area for application in the bioelectronics field.

We report a solution-phase approach to the synthesis of crystalline copper nanowires (Cu NWs) with an aspect ratio >1000 via a new catalytic mechanism comprising copper ions. The synthesis involves the reaction between copper(II) chloride and copper(II) acetylacetonate in a mixture of oleylamine and octadecene. Reaction parameters such as the molar ratio of precursors as well as the volume ratio of solvents offer the possibility to tune the morphology of the final product. A simple low-cost spray deposition method was used to fabricate Cu NW films on a glass substrate. Post-treatment under reducing gas (5% H + 95% N) atmosphere resulted in Cu NW films with a low sheet resistance of 24.5 Ω/sq, a transmittance of T = 71% at 550 nm (including the glass substrate), and a high oxidation resistance. Moreover, the conducting Cu NW networks on a glass substrate can easily be transferred onto a polycarbonate substrate using a simple hot-press transfer method without compromising on the electrical performance. The resulting flexible transparent electrodes show excellent flexibility ( R/ R < 1.28) upon bending to curvatures of 1 mm radius.

clean and renewable energy carrier, produced from sustainable and abundant energy sources, is a promising solution. [2] The combustion of hydrogen does not release any greenhouse gases into our atmosphere. [3] With focus on the photocatalytic production of hydrogen, the challenge is to find the right materials, synthesize them with the appropriate morphology and process them into a form that enables efficient photocatalysis. From a materials point of view, most of the research is dedicated to heterogeneous photocatalysis using semiconducting photo catalysts. [4] Kudo and Miseki compiled a large collection of different photocatalyst materials ranging from various metal oxides to metal (oxy)sulfides and metal (oxy)nitrides. [5] In spite of this immense compositional diversity, the largely available, cheap, stable, and nontoxic titanium dioxide (TiO 2 ) is still one of the most studied photocatalysts, regardless of its activity being limited to ultraviolet (UV) light illumination and its unfavorable fast electron hole recombination. [6] In addition to the materials selection, the morphology of the photocatalyst also plays an important role, because a large surface area, which exposes many adsorption sites to the environment, is crucial. [3] Nanostructures with particle-, [7][8][9] rod-, [10][11][12] tube-, [13][14][15] or sheet-like [16][17][18] morphology provide a large surface-to-volume ratio and thus have been found to be ideal structures for photocatalysis. However, most nanoparticles are used in powder form, which has the disadvantage that such photocatalytic nanostructures tend to agglomerate and that extraction of the photocatalyst from the reaction medium for recycling is challenging. [19] Consequently, processing of the nanoparticles into thin films [20,21] or their immobilization on 3D, photocatalytically nonactive templates such as foams, [22] sponges, [23] mesoporous silica, [24,25] electrospun nanofibers [26][27][28] or hydroxyapatite [29] has been pursued. [3] However, a significant reduction in surface area and number of adsorption sites, both of which are detrimental to photocatalytic activity, is inevitable. [19] A solution to this problem is the fabrication of templatefree, macroscopic, 3D structures entirely made of the photocatalytic material. Examples along these lines include 3D porous g-C 3 N 4 , [30] mesoporous TiO 2 foams, [31] graphene oxide (GO) sponges, [32] porous g-C 3 N 4 monoliths, [33] MoS 2 /rGO aerogels, [34] CN aerogels, [35] or Au-Pt-TiO 2 aerogels. [36] Unfortunately, the Monolithic aerogels composed of crystalline nanoparticles enable photocatalysis in three dimensions, but they suffer from low mechanical stability and it is difficult to produce them with complex geometries. Here, an approach to control the geometry of the photocatalysts to optimize their photocatalytic performance by introducing carefully designed 3D printed polymeric scaffolds into the aerogel monoliths is reported. This allows to systematically study and improve fundamental parameters in gas phase photocata...

The development of visible light-active photocatalysts is essential for increasing the conversion efficiency of solar energy into hydrogen (H2). Here, we present a facile method for nitrogen doping of monolithic titanium dioxide (TiO2) nanoparticle-based aerogels to activate them for visible light. Plasma-enhanced chemical vapor deposition at low temperature enables efficient incorporation of nitrogen into preformed TiO2 aerogels without compromising their advantageous intrinsic characteristics such as large surface area, extensive porosity, and nanoscale properties of the semiconducting building blocks. By balancing the dopant concentration and the defects, the nitridation improves optical absorption and charge separation efficiency. The nitrogen-doped TiO2 nanoparticle-based aerogels loaded with palladium (Pd) nanoparticles show a significant enhancement in visible light-driven photocatalytic H2 production (3.1 mmol h–1 g–1) with excellent stability over 5 days. With this method, we introduce a powerful tool to tune the properties of nanoparticle-based aerogels after synthesis for a specific application, as exemplified by visible light-driven H2 production.

In this paper, inorganic silica microspheres with interconnected macroporosity are tested as a platform for designing robust and efficient photocatalytic systems for a continuous flow reactor, enabling a low cost and straightforward purification of wastewater through solar‐driven photocatalysis. The photocatalytically active microspheres are prepared by wet impregnation of porous silica scaffolds with Trizma‐functionalized anatase titania (TiO 2 ) nanoparticles (NPs). NPs loading of 22 wt% is obtained in the form of a thin and well‐attached layer, covering the external surface of the microspheres as well as the internal surface of the pores. The TiO 2 loading leads to an increase of the specific surface area by 26%, without impacting the typically interconnected macroporosity ( ≈ 60%) of the microspheres, which is essential for an efficient flow of the pollutant solution during the photocatalytic tests. These are carried out in a liquid medium for the decomposition of methyl orange and paracetamol. In addition to photocatalytic activity under continuous flow, the microspheres offer the advantage that they can be easily removed from the reaction medium, which is an appealing aspect for industrial applications. In this work, the typical issues of TiO 2 NPs photocatalysts are circumvented, without the need for elaborate chemistries, and for low availability and expensive raw materials.

The use of biodegradable and nontoxic cellulose as a renewable alternative to plastic in electronics is a promising way to decrease the environmental pollution. Unfortunately, cellulose lacks one of the key properties for such applications, namely, electrical conductivity. Here, we report the complete impregnation of macroscopic cellulose fibers with copper colloids using a simple, fast, gram-scalable, electroless, and noble metal catalyst-free liquid-phase approach. By varying the stepwise addition of a precursor to the ongoing reaction, the amount of copper colloids inside the cellulose fibers and thus the electrical conductivity of the final product can be controlled. A simple vacuum filtration makes it possible to process the copper-impregnated fibers into self-supporting, paper-like membranes, whose electrical conductivity can be further improved by slight pressing. The fiber-like morphology in these papers is fully preserved after pressing, leading to a high in-plane conductivity of 10′105 ± 751 S/m. By equipping cellulose with electrical conductivity, the functional properties of this renewable material are significantly extended, making it now attractive for a wide range of emerging applications in electronics and electrocatalysis.