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Faraday Discussions

Mirabbos Hojamberdiev, Kenta Kawashima, Takashi Hisatomi, Masao Katayama, Masashi Hasegawa, Kazunari Domen, Katsuya Teshima
Factors, including crystallinity, morphology, size, preferential orientation, growth, composition, porosity, surface area, etc., can directly influence the optical, charge-separation, charge-transfer and water oxidation and reduction properties of particle-based photocatalysts. Therefore, these factors must be considered when designing high-performance particle-based photocatalysts for solar water splitting. Here, a flux growth method was applied to alter the morphology and size of Ba5Ta4O15 precursor oxide crystals using BaCl2, KCl, RbCl, CsCl, KCl + BaCl2 and K2SO4 at different solute concentrations, and the impact of nitridation with and without KCl flux was studied...
April 15, 2019: Faraday Discussions
D Buesen, T Hoefer, H Zhang, N Plumeré
Redox-active films are advantageous matrices for the immobilization of photosynthetic proteins, due to their ability to mediate electron transfer as well as to achieve high catalyst loading on an electrode for efficient generation of electricity or solar fuels. A general challenge arises from various charge recombination pathways along the light-induced electron transfer chain from the electrode to the charge carriers for electricity production or to the final electron acceptors for solar fuel formation. Experimental methods based on current measurement or product quantification are often unable to discern between the contributions from the photocatalytic process and the detrimental effect of the short-circuiting reactions...
April 15, 2019: Faraday Discussions
Jing Gao, Dan Ren, Xueyi Guo, Shaik Mohammed Zakeeruddin, Michael Grätzel
Electrochemical reduction of carbon dioxide (CO2) to multi-carbon products such as ethylene, ethanol and n-propanol offers a promising path for utilization of excessive CO2 and energy storage. Oxide-derived Cu electrodes are among the best electrocatalysts for the selective formation of ethylene and ethanol. However, a large fraction of the faradaic current still goes to hydrogen evolution, even at optimal conditions (electrolyte, potential, etc.). Here we employ the concept of sequential catalysis using judiciously designed CuAu bimetallic catalysts through galvanic exchange between Au3+ and Cu2O nanowires...
April 12, 2019: Faraday Discussions
Anastasia Vogel, Mark Forster, Liam Wilbraham, Charlotte L Smith, Alexander J Cowan, Martijn A Zwijnenburg, Reiner Sebastian Sprick, Andrew I Cooper
Conjugated ladder polymers (cLaPs) are introduced as organic semiconductors for photocatalytic hydrogen evolution from water under sacrificial conditions. Starting from a linear conjugated polymer (cLiP1), two ladder polymers are synthesized via post-polymerization annulation and oxidation techniques to generate rigidified, planarized materials bearing dibenzo[b,d]thiophene (cLaP1) and dibenzo[b,d]thiophene sulfone subunits (cLaP2). The high photocatalytic activity of cLaP1 (1307 μmol h-1 g-1) in comparison to that of cLaP2 (18 μmol h-1 g-1) under broadband illumination (λ > 295 nm) in the presence of a hole-scavenger is attributed to a higher yield of long-lived charges (μs to ms timescale), as evidenced by transient absorption spectroscopy...
April 11, 2019: Faraday Discussions
Anna Stikane, Ee Taek Hwang, Emma V Ainsworth, Samuel E H Piper, Kevin Critchley, Julea N Butt, Erwin Reisner, Lars J C Jeuken
The high quantum efficiency of natural photosynthesis has inspired chemists for solar fuel synthesis. In photosynthesis, charge recombination in photosystems is minimized by efficient charge separation across the thylakoid membrane. Building on our previous bioelectrochemical studies of electron transfer between a light-harvesting nanoparticle (LHNP) and the decahaem subunit MtrC, we demonstrate photo-induced electron transfer through the full transmembrane MtrCAB complex in liposome membranes. Successful photoelectron transfer is demonstrated by the decomposition of a redox dye, Reactive Red 120 (RR120), encapsulated in MtrCAB proteoliposomes...
April 10, 2019: Faraday Discussions
Matthias Schmalzbauer, Indrajit Ghosh, Burkhard König
The tricyclic aromatic ketone 9-anthrone and its derivatives are under basic conditions in equilibrium with their corresponding anionic forms. Unlike the neutral species, the 9-anthrolate anions can be excited by blue LED light and thus, are able to initiate a photoinduced electron transfer (PET) reaction. To demonstrate the synthetic applicability of the catalytic system, various (hetero)aryl chlorides were converted in C-C and C-Het bond-forming reactions affording the corresponding arylation products in moderate to excellent yields...
April 8, 2019: Faraday Discussions
Tessel Bouwens, Simon Mathew, Joost N H Reek
The efficiency of p-type dye-sensitized solar cells (DSSCs) remains low compared to that of n-type congeners due to charge recombination events. We report a supramolecular approach to reduce recombination at the NiO-dye interface, realized by using the cyclophane cyclobis(paraquat-p-phenylene) ring (RING4+/RING3˙+) as a redox mediator and a dye (PN) functionalized with a 1,5-dioxynaphthalene (DNP) recognition site, promoting the supramolecular formation of a pseudorotaxane capable of directing charge transfer away from the NiO-dye interface...
April 5, 2019: Faraday Discussions
Sergii I Shylin, Mariia V Pavliuk, Luca D'Amario, Igor O Fritsky, Gustav Berggren
An efficient water oxidation system is a prerequisite for developing solar energy conversion devices. Using advanced time-resolved spectroscopy, we study the initial catalytic relevant electron transfer events in the light-driven water oxidation system utilizing [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) as a light harvester, persulfate as a sacrificial electron acceptor, and a high-valent iron clathrochelate complex as a catalyst. Upon irradiation by visible light, the excited state of the ruthenium dye is quenched by persulfate to afford a [Ru(bpy)3]3+/SO4˙- pair, showing a cage escape yield up to 75%...
April 5, 2019: Faraday Discussions
Isabelle Heath-Apostolopoulos, Liam Wilbraham, Martijn A Zwijnenburg
We discuss a low-cost computational workflow for the high-throughput screening of polymeric photocatalysts and demonstrate its utility by applying it to a number of challenging problems that would be difficult to tackle otherwise. Specifically we show how having access to a low-cost method allows one to screen a vast chemical space, as well as to probe the effects of conformational degrees of freedom and sequence isomerism. Finally, we discuss both the opportunities of computational screening in the search for polymer photocatalysts, as well as the biggest challenges...
April 5, 2019: Faraday Discussions
Stelios Gavrielides, Jeannie Z Y Tan, Eva Sanchez Fernandez, M Mercedes Maroto-Valer
Anthropogenic CO2 is the main contributor to the increased concentration of greenhouse gases in the atmosphere, and thus utilising waste CO2 for the production of valuable chemicals is a very appealing strategy for reducing CO2 emissions. The catalytic fixation of CO2 with epoxides for the production of cyclic carbonates has gained increasing attention from the research community in search of an alternative to the homogeneous catalytic routes, which are currently being used in industry. A novel photocatalytic heterogeneous approach to generate cyclic carbonates is demonstrated in this work...
April 5, 2019: Faraday Discussions
Evangelos Kalamaras, Meltiani Belekoukia, Jeannie Z Y Tan, Jin Xuan, M Mercedes Maroto-Valer, John M Andresen
Utilising photoelectrochemical (PEC) devices to produce sustainable fuels from water and CO2 is a very attractive strategy, in which sunlight is used to convert the greenhouse gas (CO2) into a usable form of stored chemical energy. While significant progress has been made in the development of efficient photoactive catalysts for PEC reactions, limited efforts have been focused on the reactor design where continuous flow microfluidic PEC reactors are particular promising. In this work, a range of CuO-based thin films were used as photocathodes in a continuous flow microfluidic PEC reactor using CO2-saturated aqueous NaHCO3 solution under simulated AM 1...
April 3, 2019: Faraday Discussions
Matteo Grattieri, Kevin Beaver, Erin M Gaffney, Shelley D Minteer
The development of photobioelectrochemical systems is an exciting field requiring a combination of electrochemical, biological and material science knowledge. One of the main advantages of applying anoxygenic photosynthetic microorganisms versus non-photosynthetic bacteria is the possibility to utilize sunlight as the energy source, while removing organic contaminants from a solution. Since bacterial cells utilize energy to maintain the intracellular osmolarity, bacterial species that do not rely on organic species as an energy source have an advantage over species requiring them for their sustainment...
April 3, 2019: Faraday Discussions
Wolfgang Viertl, Johann Pann, Richard Pehn, Helena Roithmeyer, Marvin Bendig, Alba Rodríguez-Villalón, Raphael Bereiter, Max Heiderscheid, Thomas Müller, Xia Zhao, Thomas S Hofer, Mark E Thompson, Shuyang Shi, Peter Brueggeller
Inspired by natural photosynthesis, features such as proton relays have been integrated into water reduction catalysts (WRC) for effective production of hydrogen. Research by DuBois et al. showed the crucial influence of these relays, largely in the form of pendant amine functions. In this work catalysts are presented containing innovative diphosphinoamine ligands: [M(ii)Cl2(PNP-C1)], [M(ii)(MeCN)2(PNP-C1)]2+, [M(ii)(PNP-C1)2]2+, and [M(ii)Cl(PNP-C2)]+ (M = Pt2+, Pd2+, Ni2+, Co2+; PNP-C1 = N,N-bis{(di(2-methoxyphenyl)phosphino)methyl}-N-alkylamine, PNP-C2 = N,N-bis{(di(2-methoxyphenyl)phosphino)ethyl}-N-alkylamine and alkyl = Me, Et, iso-Pr, Bz)...
April 3, 2019: Faraday Discussions
Wei-Hsiang Huang, Chia-Yu Lin
Solar fuel generation using seawater as the proton source is fascinating but challenging due to the detrimental chlorochemistry, the lack of active and stable oxygen evolution catalysts operating at seawater pH (∼8) and high turnover conditions. In the present study, iron phosphate modified calcium iron oxide (CaFeOx|FePO4) modified FTO electrodes were prepared, and their electrocatalytic properties towards the oxygen evolution reaction in both synthetic and natural seawater solutions were investigated. CaFeOx|FePO4 was prepared by electrodepositing FePO4 onto CaFeOx, prepared by spin-coating and a follow-up annealing process, under a constant applied current for different durations...
April 3, 2019: Faraday Discussions
Yi-Hsuan Lai, Kai-Che Lin, Chen-Yang Yen, Bo-Jyun Jiang
We report on a simple and facile synthetic approach for preparing both a CuBi2O4 photocathode and BiVO4 photoanode from a single Bi4O5I2 nanosheet template. A nanosheet structured Bi4O5I2 (nanoBi4O5I2) template, solvothermally deposited on a conducting glass substrate, can be converted to a textured CuBi2O4 photocathode and a BiVO4 photoanode with coral-like nanostructure by drop-casting a copper ion-containing and a vanadium ion-containing solution, respectively, with a follow-up heat treatment. UV-vis absorption spectra and Mott-Schottky analyses confirm CuBi2O4 and BiVO4 have well-suited band gaps for absorbing a large portion of visible light and complementary band structures for proton reduction and water oxidation, respectively...
April 3, 2019: Faraday Discussions
David Tetzlaff, Christopher Simon, Demetra S Achilleos, Mathias Smialkowski, Kai Junge Puring, André Bloesser, Stefan Piontek, Hatice Kasap, Daniel Siegmund, Erwin Reisner, Roland Marschall, Ulf-Peter Apfel
The efficient reduction of protons by non-noble metals under mild conditions is a challenge for our modern society. Nature utilises hydrogenases, enzymatic machineries that comprise iron- and nickel- containing active sites, to perform the conversion of protons to hydrogen. We herein report a straightforward synthetic pathway towards well-defined particles of the bio-inspired material FexNi9-xS8, a structural and functional analogue of hydrogenase metal sulfur clusters. Moreover, the potential of pentlandites to serve as photocatalysts for solar-driven H2-production is assessed for the first time...
April 3, 2019: Faraday Discussions
Aubrey R Paris, Andrew B Bocarsly
Thin films of Ni3Al and Ni3Ga on carbon solid supports have been shown to generate multi-carbon products in electrochemical CO2 reduction, an activity profile that, until recently, was ascribed exclusively to Cu-based catalysts. This catalytic behavior has introduced questions regarding the role of each metal, as well as other system components, during CO2 reduction. Here, the significance of electrode structure and solid support choice in determining higher- versus lower-order reduction products is explored, and the commonly invoked Fischer-Tropsch-type mechanism of CO2 reduction to multi-carbon products is indirectly probed...
April 3, 2019: Faraday Discussions
Zeynep Kap, Ferdi Karadas
A facile synthesis for a photosensitizer-water oxidation catalyst (PS-WOC) dyad, which is connected through a polymeric platform, has been reported. The dyad assembly consists of a ruthenium-based chromophore and a cobalt-iron pentacyanoferrate coordination network as the water oxidation catalyst while poly(4-vinylpyridine) serves as the bridging group between two collaborating units. Photocatalytic experiments in the presence of an electron scavenger reveal that the dyad assembly maintains its activity for 6 h while the activity of a cobalt hexacyanoferrate and Ru(bpy)32+ couple decreases gradually and eventually decays after a 3 h catalytic experiment...
April 3, 2019: Faraday Discussions
Niclas S Mueller, Bruno G M Vieira, Dominik Höing, Florian Schulz, Eduardo B Barros, Holger Lange, Stephanie Reich
An ideal plasmonic system for hot-electron generation allows the optical excitation of plasmons, limits radiation losses, exhibits strong non-radiative electron damping, and is made from scalable and cost-effective materials. Here we demonstrate the optical excitation of dark interlayer plasmons in bilayers of colloidal gold nanoparticles. This excitation is created by an antiparallel orientation of the dipole moments in the nanoparticle layers; it is expected to exhibit strongly reduced radiative damping. Despite the vanishing dipole moment, an incoming electromagnetic wave that is propagating normal to the surface will excite the dark mode due to field retardation...
March 26, 2019: Faraday Discussions
Junyang Huang, Bart de Nijs, Sean Cormier, Kamil Sokolowski, David-Benjamin Grys, Charlie A Readman, Steven J Barrow, Oren A Scherman, Jeremy J Baumberg
External-stimuli controlled reversible formation of radical species is of great interest for synthetic and supramolecular chemistry, molecular machinery, as well as emerging technologies ranging from (photo)catalysis and photovoltaics to nanomedicine. Here we show a novel hybrid colloidal system for light-driven reversible reduction of chemical species that, on their own, do not respond to light. This is achieved by the unique combination of photo-sensitive plasmonic aggregates and temperature-responsive inorganic species generating radicals that can be finally accepted and stabilised by non-photo-responsive organic molecules...
March 13, 2019: Faraday Discussions
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