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Trigonal selenium (Se) is an elemental, direct-bandgap (1.95 eV) semiconductor with a low processing temperature, which could be a suitable top absorber for tandem solar cell applications. For incorporation in tandem architectures, both sides of the Se cell should be semitransparent.]]>Fri, 09 Jul 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=b3cb6323-3a96-4d9b-9a78-d52aa04b097bhttps://v-sustain.dtu.dk/publications/nyhed?id=af4ea6d5-0346-429b-b0f3-c3476ed363bb
Ceria is a promising material for cathodes in high-temperature CO2 electrolysis cells because ceria can become a mixed electronic and ionic conductor through doping, which enables a high surface area for electrocatalysis. Here, we systemically investigate the effect of strain to enhance the activity for electrocatalytic CO2RR on CeO2(111) using density functional theory corrected for on-site Coulomb interactions (DFT + U).]]>Thu, 08 Jul 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=af4ea6d5-0346-429b-b0f3-c3476ed363bbhttps://v-sustain.dtu.dk/publications/nyhed?id=ec85510d-0a50-46e0-8d93-945f42c33d42
Predicting activation energies for reaction steps is essential for modeling catalytic processes, but accurate barrier simulations often require considerable computational expense, especially for electrochemical reactions. Given the challenges of barrier computations and the growing promise of electrochemical routes for various processes, generalizable energetic trends in electrochemistry can significantly aid in analyzing reaction networks and building microkinetic models.]]>Thu, 03 Jun 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=ec85510d-0a50-46e0-8d93-945f42c33d42https://v-sustain.dtu.dk/publications/nyhed?id=80c1d7ce-4797-46b9-b292-12746007bb6d
High-entropy alloys (HEAs) have the potential to be a paradigm-shift for rational catalyst discovery but this new type of alloy requires a completely new approach to predict the surface reactivity. In addition to the ligand effect perturbing the surface-adsorbate bond, the random configuration of elements in the surface will also induce local strain effects due to the varying radii of neighboring atoms. Accurate modelling of HEA surface reactivity requires an estimate of this effect: To what degree is the adsorption of intermediates on these lattice distorted atomic environments affected by local strain?]]>Sat, 29 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=80c1d7ce-4797-46b9-b292-12746007bb6dhttps://v-sustain.dtu.dk/publications/nyhed?id=c3b8174b-bedf-419d-8d3a-a8d7bac98978
Determination of atomic structures is a key challenge in the fields of computational physics and materials science, as a large variety of mechanical, chemical, electronic, and optical properties depend sensitively on structure. Here, we present a global optimization scheme where energy and force information from density functional theory (DFT) calculations is transferred to a probabilistic surrogate model to estimate both the potential energy surface (PES) and the associated uncertainties. ]]>Fri, 28 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=c3b8174b-bedf-419d-8d3a-a8d7bac98978https://v-sustain.dtu.dk/publications/nyhed?id=bd52fb6d-3d54-486d-9a5e-34fd7228dcb4
Controlled electrochemical oxidation of hydrocarbons to desired products is an attractive approach in catalysis. Here we study the electrochemical propene oxidation under operando conditions using Pd L-edge X-ray absorption spectroscopy (XAS) as a sensitive probe to elucidate surface processes occurring during catalysis. ]]>Fri, 21 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=bd52fb6d-3d54-486d-9a5e-34fd7228dcb4https://v-sustain.dtu.dk/publications/nyhed?id=57f592be-cdbe-41fc-832b-9f9986b2bced
CO reduction studies over nanostructured copper catalysts are hindered by copper’s instability in alkaline conditions, which results in dissolution during immersion into the electrolyte, leading to ill-defined catalyst morphologies and loadings. Immersing catalysts under potential control can alleviate this problem, but an experimental approach for cells generally used for CO reduction experiments is lacking.]]>Fri, 14 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=57f592be-cdbe-41fc-832b-9f9986b2bcedhttps://v-sustain.dtu.dk/publications/nyhed?id=4707faa2-9c50-4db8-a8d8-2be75f8782c5
Nitric acid is manufactured by oxidizing ammonia where the ammonia comes from an energy demanding and non-eco-friendly, Haber–Bosch process. Electrochemical oxidation of N2 to nitric acid using renewable electricity could be a promising alternative to bypass the ammonia route.]]>Fri, 14 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=4707faa2-9c50-4db8-a8d8-2be75f8782c5https://v-sustain.dtu.dk/publications/nyhed?id=acabb326-4876-4a44-8cdf-3d76e72158e7
Electrochemistry–mass spectrometry is a versatile and reliable tool to study the interfacial reaction rates of Faradaic processes with high temporal resolutions. However, the measured mass spectrometric signals typically do not directly correspond to the partial current density toward the analyte due to mass transport effects.]]>Tue, 11 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=acabb326-4876-4a44-8cdf-3d76e72158e7https://v-sustain.dtu.dk/publications/nyhed?id=2d16f3ef-60e8-4b1a-9d51-4143d336e888
Oxynitride perovskites such as BaTaO2N are among the most promising materials to achieve efficient direct solar-to-chemical conversion. Albeit photoelectrochemical water splitting has been demonstrated, the required overpotentials remain prohibitively large compared with the theoretically accessible values, particularly for the oxygen evolution reaction (OER).]]>Tue, 11 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=2d16f3ef-60e8-4b1a-9d51-4143d336e888https://v-sustain.dtu.dk/publications/nyhed?id=c8a53e8c-d09c-4226-b83b-da9b7da9d4ee
A common expectation in heterogeneous catalysis is that the optimal activity will occur for the particle size with the highest concentration of undercoordinated step, edge, or corner sites, expectedly in the <5 nm range. However, many metal-catalyzed reactions follow a different trend, where the turnover frequency (TOF, here rate per surface atom) is instead lower for these smaller particles and increases strongly with increasing size toward a stabilized level with a size-independent TOF. ]]>Fri, 07 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=c8a53e8c-d09c-4226-b83b-da9b7da9d4eehttps://v-sustain.dtu.dk/publications/nyhed?id=162051ab-a7e4-4c02-9ea9-840248cae2c4
Ligand and strain effects can tune the adsorption energy of key reaction intermediates on a catalyst surface to speed up rate-limiting steps of the reaction. As novel fields like high-entropy alloys emerge, understanding these effects on the atomic structure level is paramount: What atoms near the binding site determine the reactivity of the alloy surface? By statistical analysis of 2000 density functional theory calculations and subsequent host/guest calculations, it is shown that three atomic positions in the third layer of an fcc(111) metallic structure fourth-nearest to the adsorption site display significantly increased influence on reactivity over any second or third nearest atomic positions. ]]>Wed, 05 May 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=162051ab-a7e4-4c02-9ea9-840248cae2c4https://v-sustain.dtu.dk/publications/nyhed?id=7b11092f-9231-4db0-91c7-6697343dc5ae
As electrochemical CO2 reduction studies progress from beaker or H-cell devices operating at low current densities to gas diffusion electrode (GDE)-based devices that sustain high reaction rates and provide an avenue toward commercialization, the overall system becomes significantly more complex. While the current densities may vary for the different approaches, it is essential to maintain the same scientific rigor when analyzing these systems. ]]>Fri, 23 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=7b11092f-9231-4db0-91c7-6697343dc5aehttps://v-sustain.dtu.dk/publications/nyhed?id=7f59b833-5d9b-4a16-9162-cea9ee92d029
In this study, we use density functional theory to investigate the catalytic activity of graphene (G), single vacancy defective graphene (GSV), quaternary N-doped graphene (NGQ), and pyridinic N-doped graphene (NGpy, 3NGpy, and 4NGpy) on Co(0001) substrate for an oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFCs). ]]>Thu, 15 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=7f59b833-5d9b-4a16-9162-cea9ee92d029https://v-sustain.dtu.dk/publications/nyhed?id=23eae91c-3941-4159-aa27-bb18d44cb16d
The search for cheap and abundant alternatives to Pt for the hydrogen evolution reaction (HER) has led to many efforts to develop new catalysts. Although the discovery of promising catalysts is often reported, none can compete with Pt in intrinsic activity. To enable true progress, a rigorous assessment of intrinsic catalytic activity is needed, in addition to minimizing mass-transport limitations and following best practices for measurements. ]]>Fri, 09 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=23eae91c-3941-4159-aa27-bb18d44cb16dhttps://v-sustain.dtu.dk/publications/nyhed?id=b3d46078-6792-4eef-80fb-709c83ebf5d9
We use density functional theory, molecular dynamics, and metadynamics to study electrochemical *CO–*CO coupling in explicit electrolyte. We consider both the *CO–*CO coupling reaction and the charging process required to keep the potential constant. The charging process consists of transferring explicit cations from the electrolyte and electrons from the potentiostat to the interface. ]]>Fri, 02 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=b3d46078-6792-4eef-80fb-709c83ebf5d9https://v-sustain.dtu.dk/publications/nyhed?id=3538177e-0e1b-45b1-9ec9-aba38e6968c2
Electrocatalysis on high-entropy alloys (HEAs) is a very young field. There are only a few articles on the theoretical understanding of catalysis on these surfaces. Activity descriptors and a ‘theory of catalysis’ exist for uniform surfaces.]]>Thu, 01 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=3538177e-0e1b-45b1-9ec9-aba38e6968c2https://v-sustain.dtu.dk/publications/nyhed?id=24856a13-51f7-4bbc-ac88-8a8f7e499708
]]>Thu, 01 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=24856a13-51f7-4bbc-ac88-8a8f7e499708https://v-sustain.dtu.dk/publications/nyhed?id=0ed108aa-121d-4709-91d5-3653ebb04a89
]]>Thu, 01 Apr 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=0ed108aa-121d-4709-91d5-3653ebb04a89https://v-sustain.dtu.dk/publications/nyhed?id=eb68ba5d-562a-4a17-bfb4-f3b65de5dfe9
In heterogeneous catalysis, free energy profiles of reactions govern the mechanisms, rates, and equilibria. Energetics are conventionally computed using the harmonic approximation (HA), which requires determination of critical states a priori. Here, we use neural networks to efficiently sample and directly calculate the free energy surface (FES) of a prototypical heterogeneous catalysis reaction—the dissociation of molecular nitrogen on ruthenium—at density-functional-theory-level accuracy.]]>Thu, 25 Mar 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=eb68ba5d-562a-4a17-bfb4-f3b65de5dfe9https://v-sustain.dtu.dk/publications/nyhed?id=51e80bb6-ba01-4ac4-84ee-cbfc27336572
Complex solid solutions (“high entropy alloys”), comprising five or more principal elements, promise a paradigm change in electrocatalysis due to the availability of millions of different active sites with unique arrangements of multiple elements directly neighbouring a binding site. Thus, strong electronic and geometric effects are induced, which are known as effective tools to tune activity.]]>Mon, 22 Mar 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=51e80bb6-ba01-4ac4-84ee-cbfc27336572https://v-sustain.dtu.dk/publications/nyhed?id=c4d3ec61-9ee4-4f77-9af5-1c7648911682
Aiming at a better understanding of the role of electronic / chemical modifications of the support on the performance of high specific surface area Ru/TiO2 catalysts in the selective CO methanation, we prepared and examined four different Ru/TiO2 catalysts with similar Ru loading and similar high specific surface area, but with the support doped with different amounts of Si (0–12 wt.% SiO2). ]]>Mon, 01 Mar 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=c4d3ec61-9ee4-4f77-9af5-1c7648911682https://v-sustain.dtu.dk/publications/nyhed?id=34173b51-c5f3-4aaa-8ed6-179007d6d65f
Photoelectrochemical (PEC) water splitting devices replace electrical contacts in a solid-state solar cell with a solid/liquid junction to improve the solar-to-H2conversion efficiency and reduce system cost. The wireless configuration can fully use the advantage of the PEC by removing all electrical contacts; however, the wired configuration with the electrical contact on its back side has been widely studied to facilitate device characterization. ]]>Wed, 24 Feb 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=34173b51-c5f3-4aaa-8ed6-179007d6d65fhttps://v-sustain.dtu.dk/publications/nyhed?id=855343f5-a1a8-4f02-b89e-090d0663bab6
Cu electrodes are promising materials to catalyze the conversion of CO2 and CO into renewable fuels and valuable chemicals. However, a detailed description of the properties of the Cu–electrolyte interface is still crucial to reach a complete understanding of the CO reduction mechanism. Herein, we have investigated the interfacial properties of Cu(111) and Cu(100) in phosphate buffer solutions at different pH conditions and in the presence of CO. Ab initio molecular simulations of the Cu–electrolyte interface were combined with voltammetric experiments carried out on Cu(100) and Cu(111) single-crystalline electrodes. ]]>Fri, 05 Feb 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=855343f5-a1a8-4f02-b89e-090d0663bab6https://v-sustain.dtu.dk/publications/nyhed?id=bf7abcc3-f4a0-4539-b76c-e8002beeb4d2
A challenge in the electrochemical CO2 reduction reaction (CO2RR) is the lack of efficient and selective electrocatalysts to valuable chemicals. Hydrocarbons and valuable chemicals from the CO2RR have primarily been observed on metallic Cu. Here, 3D carbon electrocatalysts (diporphyrin molecules; i.e., Pacman) have been investigated as potential CO2RR electrocatalysts using density functional theory simulations.  ]]>Fri, 15 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=bf7abcc3-f4a0-4539-b76c-e8002beeb4d2https://v-sustain.dtu.dk/publications/nyhed?id=7a6bff5c-f9da-422e-b308-d91a886c703f
Infrared spectroscopy on CO chemisorbed on Raney Cu and materials with Cu dispersed as nanoparticles on oxide supports was used to evaluate support effects on the Cu surface properties. The C-O frequency (νC-O) is sensitive to the charge on the adsorption site with νC-O being high on Cu+, intermediate on Cu0, and low on Cu−, whereby this method can probe the charging state of the Cu surface. The Raney Cu reference demonstrates the complex analysis of the IR band intensity, which can be susceptible to dipole coupling. ]]>Mon, 04 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=7a6bff5c-f9da-422e-b308-d91a886c703fhttps://v-sustain.dtu.dk/publications/nyhed?id=c098a73b-a06e-4fb2-afa1-c532e78c9cf2
Discovering low-cost, durable and highly active electrocatalysts with reduced use of precious platinum group metals (PGM) as catalysts for the hydrogen evolution reaction (HER), the oxygen reduction reaction (ORR), and the oxygen evolution reaction (OER) is a key step for large-scale adaptation of fuel cells, electrolyzers, and metal-air batteries. Here we explore the stability and reaction mechanisms of synthesized one-dimensional transition metal dithiolene wire (TM-DWs, TM = Cr – Cu, Rh, Ir, Pt, Pd) for the ORR and the OER in acid solution by density functional theory (DFT) calculations. Our calculations reveal that Co-DW intrinsically exhibits high catalytic activity for bi-functional ORR/OER with low limiting overpotentials (η) of 0.46/0.45 V via four-electron reactions. ]]>Mon, 04 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=c098a73b-a06e-4fb2-afa1-c532e78c9cf2https://v-sustain.dtu.dk/publications/nyhed?id=f58ad8d2-66da-4e59-8f8b-8a62ca482a5f
Metal and nitrogen co-doped carbons (M-N/Cs) are promising alternatives to platinum-based catalysts for the oxygen reduction reaction (ORR). Here, density functional theory calculations are used to compare the ORR activity of Co single and double sites embedded in N-doped carbon. Two different models of a Co double site are investigated, one in which two single sites are stacked on top of each other and one which has two Co atoms next to each other in a single graphene sheet. ]]>Mon, 04 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=f58ad8d2-66da-4e59-8f8b-8a62ca482a5fhttps://v-sustain.dtu.dk/publications/nyhed?id=9ba6b36b-19ab-4381-a334-3410b0d24095
Single-atom catalysts (SACs) have recently attracted broad scientific interests due to their unique structural feature, the single-atom dispersion. Optimized electronic structure as well as high stability are required for single-atom catalysts to enable efficient electrochemical production of H2O2. ]]>Mon, 04 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=9ba6b36b-19ab-4381-a334-3410b0d24095https://v-sustain.dtu.dk/publications/nyhed?id=aced97a9-779d-47eb-8071-95bd493c96f7
The roles of CO and CO2 in Cu-catalyzed methanol synthesis from syngas were evaluated in experiments with gas switching between CO/H2 and CO2/H2 feeds and between a CO2/CO/H2 feed and a corresponding CO-free CO2/inert/H2 feed. Switching between CO/Ar/H2 (3/29/68) and CO2/N2/H2 (3/29/68) for Cu/Al2O3 showed that the rate of methanol synthesis on Cu is more than an order of magnitude higher from CO2 compared to CO. Experiments switching between CO2/CO/H2 and CO2/inert/H2 showed that at low conversion conditions with negligible product formation, CO is purely inhibiting for Raney Cu and for a range of supported (on SiO2, TiO2, Al2O3 and ZnO) Cu-catalysts including an industrial-type Cu/ZnO/Al2O3 catalyst. Given the generality across Cu-based samples the mechanism of this inhibition is most likely competitive adsorption of CO on the Cu surface. ]]>Mon, 04 Jan 2021 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=aced97a9-779d-47eb-8071-95bd493c96f7https://v-sustain.dtu.dk/publications/nyhed?id=cd6ab1b8-fc85-4b82-b6b1-52a1d4c076f5
Electrochemical reduction of nitrogen to ammonia can potentially replace the existing centralized fossil fuel-based Haber–Bosch process with small, decentralized units relying on electrical energy from renewable sources, thus supporting a sustainable food and energy infrastructure. Recent activities in the development of transition metal nitride electrocatalysts for this reaction have shown promise, but oxynitrides remain unexplored. We have performed a rigorous computational study of the highly promising vanadium oxynitride (VON) to establish for the first time the nitrogen reduction pathway in oxynitrides and the role of the mixed anions that can lead to improved stability of the active surface-states, activity, and selectivity over hydrogen evolution.]]>Mon, 02 Nov 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=cd6ab1b8-fc85-4b82-b6b1-52a1d4c076f5https://v-sustain.dtu.dk/publications/nyhed?id=7c53f7a9-806d-49e5-9118-97aada9c34d3
We perform a computational screening for two-dimensional (2D) magnetic materials based on experimental bulk compounds present in the Inorganic Crystal Structure Database and Crystallography Open Database. A recently proposed geometric descriptor is used to extract materials that are exfoliable into 2D derivatives and we find 85 ferromagnetic and 61 antiferromagnetic materials for which we obtain magnetic exchange and anisotropy parameters using density functional theory. ]]>Wed, 21 Oct 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=7c53f7a9-806d-49e5-9118-97aada9c34d3https://v-sustain.dtu.dk/publications/nyhed?id=f08ac12b-4aeb-4587-a5fd-6f7f88cd8343
hemical hydrogen adsorption and desorption, and the state of adsorbed hydrogen (*H) on metal surfaces are of fundamental interest as well as practical importance for the hydrogen evolution reaction (HER) and electrochemical hydrogenation reactions including CO2 and CO electroreduction. Here, we report a previously undiscovered phenomenon whereby *H desorbs as H2 during an anodic potential sweep at potentials anodic of (more positive than) the equilibrium potential of U0(H2/H+), hence at potentials where hydrogen desorption would be expected as H+. ]]>Wed, 21 Oct 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=f08ac12b-4aeb-4587-a5fd-6f7f88cd8343https://v-sustain.dtu.dk/publications/nyhed?id=3ce68c84-745f-49a2-851b-fd410ea7dada
Various thin-film I2–II–IV–VI4 photovoltaic absorbers derived from kesterite Cu2ZnSn(S,Se)4 have been synthesized, characterized, and theoretically investigated in the past few years. The availability of this homogeneous materials dataset is an opportunity to examine trends in their defect properties and identify criteria to find new defect-tolerant materials in this vast chemical space. We find that substitutions on the Zn site lead to a smooth decrease in band tailing as the ionic radius of the substituting cation increases. ]]>Thu, 01 Oct 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=3ce68c84-745f-49a2-851b-fd410ea7dadahttps://v-sustain.dtu.dk/publications/nyhed?id=2f1aaad0-247b-4586-91db-74e4c8f2890f
Cyclic voltammograms are key to much of the accumulated understanding of the nature of electrochemical interfaces; however, they provide no direct information on the atomic structure of the interface. Herein, we present a method allowing for the direct coupling of ab initio simulations to experiments and vice versa. The methodology proposed is based on the use of the generalized computational hydrogen electrode, which herein has been further developed to account for counterions.]]>Thu, 17 Sep 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=2f1aaad0-247b-4586-91db-74e4c8f2890fhttps://v-sustain.dtu.dk/publications/nyhed?id=46473e8d-8120-43bb-ba33-f1a194d91100
In this work, the effect of ion-selective membranes on the detailed carbon balance was systematically analyzed for high-rate CO2 reduction in GDE-type flow electrolyzers.]]>Mon, 07 Sep 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=46473e8d-8120-43bb-ba33-f1a194d91100https://v-sustain.dtu.dk/publications/nyhed?id=094440b2-cc3b-4357-a936-fa0feef0b6c0
Alloys of platinum and lanthanides present a remarkable activity for the oxygen reduction reaction—both in the form of extended surfaces and nanoparticulate catalysts. Co-sputter-deposited thin film catalysts based on platinum and gadolinium show great oxygen reduction activity improvement over pure Pt. ]]>Mon, 31 Aug 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=094440b2-cc3b-4357-a936-fa0feef0b6c0https://v-sustain.dtu.dk/publications/nyhed?id=3d01cb83-f255-42e3-a119-5f8f5757379e
Several concepts for platinum-based catalysts for the oxygen reduction reaction (ORR) are presented that exceed the US Department of Energy targets for Pt-related ORR mass activity. Most concepts achieve their high ORR activity by increasing the Pt specific activity at the expense of a lower electrochemically active surface area (ECSA).]]>Mon, 24 Aug 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=3d01cb83-f255-42e3-a119-5f8f5757379ehttps://v-sustain.dtu.dk/publications/nyhed?id=ed43b201-ba3b-4f4f-9fb3-5d55d8ddf37d
Catalytic methanol synthesis is one of the major processes in the chemical industry and may grow in importance, as methanol produced from CO2 and sustainably derived H2 are envisioned to play an important role as energy carriers in a future low‐CO2‐emission society. However, despite the widespread use, the reaction mechanism and the nature of the active sites are not fully understood. ]]>Thu, 13 Aug 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=ed43b201-ba3b-4f4f-9fb3-5d55d8ddf37dhttps://v-sustain.dtu.dk/publications/nyhed?id=6a4fd3d8-6ded-4a06-9c3b-7446626b4683
Ceria has attracted considerable interest for the high-temperature electrocatalytic water splitting reaction (WSR) in solid oxide electrolysis cells (SOECs) due to the large active surface area enabled by its accessibility to ions, electrons and gas molecules. The mechanism of the WSR on the (1 1 1) facet of ceria has been studied extensively and hydroxyl decomposition is widely reported as the rate-determining step. However, WSR on other most-often exposed low-index surfaces like CeO2(1 1 0) and CeO2(1 0 0) remains unclear, especially the effect of high temperature on the formation of hydroxyls with different hydrogen coverage (circle minus(H)) and reaction pathways. ]]>Sat, 01 Aug 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=6a4fd3d8-6ded-4a06-9c3b-7446626b4683https://v-sustain.dtu.dk/publications/nyhed?id=c0badda5-0846-42e1-a851-397e79c2ba92
Iron–nitrogen-doped graphene (FeNC) has emerged as an exciting earth-abundant catalyst for electrochemical CO2 reduction (CO2R). However, standard theoretical approaches based on density functional theory (DFT) suggest complete poisoning of the active sites and are unable to rationalize the experimentally observed dramatic pH dependence and Tafel slopes, which have a critical impact on the electrocatalytic activity. ]]>Fri, 17 Jul 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=c0badda5-0846-42e1-a851-397e79c2ba92https://v-sustain.dtu.dk/publications/nyhed?id=e7eea7bc-4f45-4b1b-8349-2a119372e1c4
The recirculation of gases in a sealed reactor system is a broadly useful method in catalytic and electrocatalytic studies. It is especially relevant when a reactant gas reacts slowly with respect to residence time in a catalytic reaction zone and when mass transport control through the reaction zone is necessary. This need is well illustrated in the field of electrocatalytic N2 reduction, where the need for recirculation of 15N2 has recently become more apparent. ]]>Tue, 14 Jul 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=e7eea7bc-4f45-4b1b-8349-2a119372e1c4https://v-sustain.dtu.dk/publications/nyhed?id=9831ee2a-33a4-4c6b-a5e2-179e2cba5c77
In this work, we develop a new microkinetic model for the oxygen reduction reaction (ORR) which incorporates field effects into the established computational hydrogen electrode model. We find that the field can significantly alter the binding energy of ORR adsorbates, particularly *OOH, *O2, and *H2O2. ]]>Thu, 09 Jul 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=9831ee2a-33a4-4c6b-a5e2-179e2cba5c77https://v-sustain.dtu.dk/publications/nyhed?id=04cfedc5-b072-45cf-a6df-099056c93b42
A screening study of the catalytic performance of ternary alloy nanoparticles containing nickel, iron and gallium supported on silica for methanol synthesis from CO2 and H2 was performed. Catalysts were prepared by incipient wetness impregnation and subsequently reduced in H2 before catalytic testing. Ni2FeGa showed the best performance of the tested catalysts in terms of methanol yield.]]>Thu, 18 Jun 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=04cfedc5-b072-45cf-a6df-099056c93b42https://v-sustain.dtu.dk/publications/nyhed?id=1b180256-4f86-48a2-88c1-16d76b64692d
Understanding the nature of active sites is central to controlling (electro)catalytic activity. Here we employed surface X-ray scattering coupled with density functional theory and surface-enhanced infrared absorption spectroscopy to examine the oxygen evolution reaction on RuO2 surfaces as a function of voltage. ]]>Wed, 10 Jun 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=1b180256-4f86-48a2-88c1-16d76b64692dhttps://v-sustain.dtu.dk/publications/nyhed?id=5f0908df-61d0-4363-b72e-a825f6edc9b4
In the past decade, the mass activity of catalysts for the oxygen reduction reaction (ORR) has been improved mainly via increasing the number of active sites. However, little progress has been made on the improvement of the intrinsic activity of ORR catalysts; consequently, the widespread use of fuel cells is still limited by low energy efficiency.   ]]>Fri, 05 Jun 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=5f0908df-61d0-4363-b72e-a825f6edc9b4https://v-sustain.dtu.dk/publications/nyhed?id=4b857d73-c8de-4bdc-a5f9-224d008ab86f
Electrochemical transformation of potent greenhouse gases such as CO2 and CH4 to produce useful carbon-based products is a highly desirable sustainability goal. However, selectivity challenges remain in aqueous electrochemical processes as selective CO2 reduction to desired products is difficult and electrochemical CH4 oxidation often proceeds at very low rates. The formation of C–C coupled products in these fields is particularly desirable as this provides a path for the production of high-value fuels and chemicals. We have developed a cyclic electrochemical strategy which can produce acetylene, a C–C coupled product, from such carbon sources and water, with favorable current density and selectivity. ]]>Mon, 01 Jun 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=4b857d73-c8de-4bdc-a5f9-224d008ab86fhttps://v-sustain.dtu.dk/publications/nyhed?id=ff2511ca-cd60-4591-971d-d3a405198725
The bismuth-based (oxy)iodides BiI3, BiOI, and AgxBiIx+3 share similar layered crystal structures, optimal band gaps for top absorbers in tandem solar cells, and moderate synthesis temperatures. Similarly to halide perovskite absorbers, they contain a heavy cation with a lone pair of electrons (Bi3+), which has been proposed as an important feature enabling defect tolerance in perovskites. The aim of this work is to grow and characterize BiI3, BiOI, and Ag3BiI6 absorbers and solar cells using a consistent synthesis and analysis routine. In this way, the individual strengths and weaknesses of the three absorbers, as well as their common challenges, can be outlined.]]>Tue, 28 Apr 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=ff2511ca-cd60-4591-971d-d3a405198725https://v-sustain.dtu.dk/publications/nyhed?id=77c4aebf-3d8c-40f1-af08-e7685b6647f7
The lithium–sulfur (Li–S) battery is widely regarded as a promising energy storage device due to its low price and the high earth‐abundance of the materials employed. However, the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox conversion result in inefficient sulfur utilization, low power density, and rapid electrode deterioration. Herein, these challenges are addressed with two strategies 1) increasing LiPS conversion kinetics through catalysis, and 2) alleviating the shuttle effect by enhanced trapping and adsorption of LiPSs. ]]>Mon, 27 Apr 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=77c4aebf-3d8c-40f1-af08-e7685b6647f7https://v-sustain.dtu.dk/publications/nyhed?id=181a1a4a-626c-4a7a-b37b-db272749f616
Rationalizing the influence of the solvent on electrochemical reaction energetics is a central challenge in our understanding of electrochemical interfaces. To date, it is unclear how well existing methods predict solvation energies at solid/liquid interfaces since they cannot be assessed experimentally. Ab initio molecular dynamics (AIMD) simulations present a physically highly accurate, but also a very costly approach. In this work, we employ extensive AIMD simulations to benchmark solvation at charge-neutral metal/water interfaces against commonly applied continuum solvent models. ]]>Tue, 14 Apr 2020 08:00:00 +0200https://v-sustain.dtu.dk/publications/nyhed?id=181a1a4a-626c-4a7a-b37b-db272749f616