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We examined the regional electrophysiologic effects of successful and unsuccessful direct-current cardioversion shocks on different right and left atrial regions in patients with sustained atrial fibrillation (AF). Patients with sustained AF undergoing external cardioversion underwent simultaneous mapping of the right and left atria. Electrogram changes after shock delivery, regional atrial activation, and effects of shock intensity were analyzed. Twenty-two patients with sustained AF received 52 shocks (mean 2.4/patient, 22 successful and 30 unsuccessful). The efficacy of 50, 100, 200, and 300 J was 18%, 39%, 100%, and 100%, respectively. In all 22 successful shocks, there was virtually simultaneous termination of electrical activity in all right and left atrial regions mapped. Unsuccessful shocks resulted in a significant increase in mean atrial cycle length at lateral right atrium, superior left atrium, and proximal, mid, and distal coronary sinus (p = 0.01), but not at the interatrial septum (p >0.2), which often disappeared before the next shock. This cycle length prolongation was accompanied by reduction in fragmented and chaotic electrograms (p <0.03) and emergence of discrete electrograms at all right and left atrial regions that persisted until the next shock. The changes in electrogram morphology failed to alter the surface electrocardiographic appearance of AF. There was no correlation between the shock intensity and the magnitude of these effects. We conclude that termination of AF with external cardioversion shocks is associated with the widespread extinction of regional atrial wave fronts. Unsuccessful shocks are associated with a temporary slowing of atrial activation at all regions except at the interatrial septum and emergence of organized and/or rapidly propagating wave fronts. [ABSTRACT FROM AUTHOR]

We performed simultaneous catheter mapping of right and left atrial regions at onset and during sustenance of spontaneous atrial fibrillation (AF) in patients with ischemic and/or hypertensive heart disease. Seventeen patients with structural heart disease had spontaneous and electrically induced AF episodes mapped from their onset simultaneously in multiple right and left atrial regions. Atrial premature complexes (APCs) that initiated spontaneous AF had coupling intervals ranging from 260 to 400 ms (mean 332 +/- 61), most commonly arising from the lateral right atrium (31%), right atrioventricular junction (13%), atrial septum (6%), superior left atrium (25%), or inferior left atrium (25%). APC morphology on surface electrocardiograms did not correlate with origin in specific atrial regions. The earliest regions of atrial activation for the first AF cycle were the lateral right atrium (n = 5), superior left atrium (n = 4), distal or mid coronary sinus (n = 4), atrial septum (n = 2), and right atrioventricular junction at the His bundle location (n = 2). Spontaneous AF at onset usually showed discrete but irregular electrograms at virtually all right and left atrial sites mapped, with a reproducible region of AF initiation in all 8 patients with multiple events. The region of earliest atrial activation at spontaneous AF onset was in close proximity to the APC origin in 15 of 16 patients (94%), and 39 of 40 episodes (97%) mapped. Stable patterns of right and left atrial activation were observed at AF onset in 14 patients. Induced AF elicited with right atrial stimulation demonstrated different sites of earliest regional atrial activation at onset compared with spontaneous AF events in 4 of 8 patients. However, discrete intracardiac electrograms were also present in induced AF in all of the mapped atrial regions. Furthermore, the site of extrastimulus delivery in induced AF was also found to be in close proximity to the earliest region of atrial activation for the first AF beat. We conclude that spontaneous AF is initiated by APCs arising in different right or left atrial regions in patients with structural heart disease and the initial region of atrial activation in AF is in proximity to the region of APC origin. Organized and repetitive electrical activation is frequently observed in both right and left atria at AF onset. Although electrically induced AF may have different activation patterns than spontaneous AF at onset in many patients, both types of AF demonstrate organization and earliest atrial activation in proximity to the initiating APC. [ABSTRACT FROM AUTHOR]

We analyzed the patterns of atrial activation and characterized the electrophysiologic properties of regional atrial sites in the, right atrium and left atrium at the onset of atrial fibrillation (AF) induced with programmed right atrial (RA) stimulation. Intraatrial conduction, atrial electrogram return cycle lengths for the first AF cycle, RA and left atrial (LA) activation maps during AF, and the stability and reproducibility of atrial activation sequences at AF onset and maintenance were analyzed in 23 patients with AF. Correlation of intracardiac electrograms with surface electrocardiographic morphology was attempted. Maximum intraatrial conduction delay for high RA premature beats was observed at the coronary sinus ostium (n = 15), His bundle region (n = 13) or interatrial septum (n = 15). The return cycle lengths for the first AF cycle showed increasing conduction delay with increasing prematurity of the last extrastimulus in most patients. Suprisingly, discrete atrial electrograms with regular or irregular cycle lengths were present at the onset of electrocardiographic documented coarse AF in 13 of 15 patients (87%). Fragmented or chaotic atrial activity were present in 2 of 15 patients (13%) in coarse AF but observed at > or = 1 atrial sites in 7 of 8 patients (88%) with fine AF (p = 0.001). The atrial activation sequence at the onset of the induced AF elicited by high RA extrastimuli usually showed the earliest activation site at the crista terminalis (9 patients) or interatrial septum (9 patients). In contrast, induced AF elicited from other RA sites usually showed earliest atrial activation at the septum (3 patients) or coronary sinus ostium (3 patients). Atrial activation sequences for the first induced AF cycle were usually reproducible in most patients. Atrial activation patterns during the first 10 cycles for AF were stable in RA and LA regions in 6 of 23 patients (260%) but demonstrated significant change(s) at > or = 1 region in 17 of 23 patients (74%) (p <0.05). We conclude that pacing induced AF elicited by RA premature beats commences as a regular or irregular rapid atrial tachycardia consistent with a transitional, but often organized, arrhythmia. The activation sequence and electrophysiologic behavior of the first induced AF cycle is consistent with intraatrial reentry and reproducible in most patients. More than 1 atrial activation sequence can sometimes be observed, emphasizing the dynamic nature of the initial RA reentrant circuits. [ABSTRACT FROM AUTHOR]

We examined the activation of the right atrium and left atrium by pacing from different atrial sites using several single- and dual-site atrial pacing modes in patients with atrial fibrillation or flutter. We also analyzed the effect of these pacing modes on fixed coupled extrastimuli in this population. Patients underwent detailed mapping of regional right atrial (RA) and left atrial (LA) sites. Bipolar pacing was performed individually from the high right atrium, coronary sinus ostium, and the distal coronary sinus, and simultaneously from the high right atrium and coronary sinus ostium (dual-site RA pacing) or high right atrium and distal coronary sinus (biatrial pacing). Extrastimuli were delivered from the high right atrium at fixed coupling intervals of 350 and 250 ms. Twenty patients with atrial fibrillation were studied. P-wave duration during pacing was significantly abbreviated by both dual-site RA and biatrial pacing (p <0.001 vs high RA pacing, respectively) but not by any other single-site atrial pacing method. Both dual-site atrial pacing modes also significantly abbreviated P wave durations for closely coupled high RA premature beats (p <0.001) in contrast to high RA pacing. During the basic pacing drive and for high RA extrastimuli, RA activation at the crista terminalis and atrial septum was comparable in sinus rhythm, high RA pacing, and in both dual-site atrial pacing methods, but was significantly delayed by coronary sinus ostial and distal coronary sinus pacing. In contrast, proximal coronary sinus activation was delayed with high RA pacing compared with all other pacing modes, and high RA extrastimuli encountered reduced conduction delay at this location with dual-site atrial pacing modes. LA activation was advanced superiorly by both single-site coronary sinus pacing methods and both dual-site atrial pacing techniques. Inferior and lateral LA activation was advanced by all pacing modes using a coronary sinus pacing site. However, earlier activation of LA sites occurred for high RA premature beats after both dual-site pacing methods (p <0.05) compared with single-site pacing modes. Incremental conduction delay at different atrial regions for closely coupled high RA extrastimuli ranged from 33% to 120% during high RA pacing and was significantly attenuated at multiple RA and LA sites by dual-site RA and biatrial pacing. Distinct global, as well as regional electrophysiologic effects, may mediate the variable antiarrhythmic effects of different and novel atrial pacing methods. [ABSTRACT FROM AUTHOR]

This report illustrates the complexity of internal atrial defibrillation and implantable cardioverter-defibrillator therapy in patients with dual site atrial pacing systems. [ABSTRACT FROM AUTHOR]

Calculated thermodynamic properties for the electrochemical glycerol oxidation at different temperatures and potentials indicate that external applied bias has a more significant influence on reaction selectivity than temperature.

Background and study aims Patients with symptomatic cholelithiasis can be stratified according to the 2019 European Society for Gastrointestinal Endoscopy (ESGE) guideline into low-, intermediate- and high-likelihood groups for presence of choledocholithiasis. For the intermediate group, endoscopic ultrasound (EUS) or magnetic resonance cholangiopancreatography (MRCP) is recommended to assess whether an endoscopic retrograde cholangiopancreatography (ERCP) is necessary prior to cholecystectomy. The aim of the study was to investigate adherence to the guideline for diagnostic and treatment strategy for cholelithiasis in daily clinical practice. Patients and methods A multicenter, retrospective cross-sectional observational study of the diagnostic pathway of patients with suspicion of choledocholithiasis was conducted between 2019 and 2021. Patients were stratified according to the ESGE guideline "Endoscopic management of common bile duct stones". Results A total of 305 patients were included in the analysis and stratified into low- (17%), intermediate- (40%) and high- (43%) likelihood of choledocholithiasis. In these three categories, 182 patients (60%) underwent ERCP. Adherence to the ESGE guideline recommendation was 59.7% overall and was the highest in the intermediate-likelihood group (83.6%), compared with 45.1% in the low- and 43.2% in the high-likelihood group, respectively ( P < 0.001). In the high-likelihood group, 49% underwent additional imaging. In 195 patients who underwent additional imaging, 55 ERCPs (28.2%) could be avoided. Conclusions This study shows that stratification according to the ESGE guideline is useful to reduce the number of unnecessary additional imaging procedures and ERCPs in patients with a suspicion of choledocholithiasis. It seems worthwhile to perform EUS prior to ERCP in the same session., Competing Interests: Conflict of Interest Mike J.P. de Jong, Megan M.L. Engels, Christina J. Sperna Weiland, Robin Krol, Tanya M. Bisseling and Foke van Delft have no conflicts of interest or financial ties to disclose. Jeanin E. van Hooft reports lecture fees from Cook Medical, dr. Falk Pharma, Boston Scientific, AbbVie, and consultancy fees from Olympus. Erwin M. van Geenen reports research grants from Olympus, Boston Scientific, and MTW Endoskopie. Peter D. Siersema reports research grants from Pentax and Fujifilm. All outside the submitted work., (The Author(s). This is an open access article published by Thieme under the terms of the Creative Commons Attribution License, permitting unrestricted use, distribution, and reproduction so long as the original work is properly cited. (https://creativecommons.org/licenses/by/4.0/).)

Photoelectrochemical (PEC) water splitting is a promising approach for sustainable hydrogen production. Previous studies have focused on devices operated at atmospheric pressure, although most applications require hydrogen delivered at elevated pressure. Here, we address this critical gap by investigating the implications of operating PEC water splitting directly at elevated pressure. We evaluate the benefits and penalties associated with elevated pressure operation by developing a multiphysics model that incorporates empirical data and direct experimental observations. Our analysis reveals that the operating pressure influences bubble characteristics, product gas crossover, bubble-induced optical losses, and concentration overpotential, which are crucial for the overall device performance. We identify an optimum pressure range of 6-8 bar for minimizing losses and achieving efficient PEC water splitting. This finding provides valuable insights for the design and practical implementation of PEC water splitting devices, and the approach can be extended to other gas-producing (photo)electrochemical systems. Overall, our study demonstrates the importance of elevated pressure in PEC water splitting, enhancing the efficiency and applicability of green hydrogen generation., (© 2024. The Author(s).)

Glycerol, a primary by-product of biodiesel production, can be oxidized into various value-added chemicals, significantly enhancing the techno-economic value of photoelectrochemical (PEC) cells. Several studies have explored various photoelectrode materials and co-catalysts, but the influence of electrolytes on PEC glycerol oxidation has remained relatively unexplored despite its significance. Here, we explore the impact of various acidic (pH = 2) electrolytes, namely NaNO 3 , NaClO 4 , Na 2 SO 4 , K 2 SO 4 , and KP i , on PEC glycerol oxidation using nanoporous thin film BiVO 4 as a model photoanode. Our experimental findings reveal that the choice of electrolyte anion and cation significantly affects the PEC performance ( i.e. , photocurrent, onset potential, stability, and selectivity towards value-added products) of BiVO 4 for glycerol oxidation. To explain this interesting phenomenon, we correlate the observed performance trend with the ion specificity in the Hofmeister series as well as the buffering capacity of the electrolytes. Notably, NaNO 3 is identified as the optimal electrolyte for PEC glycerol oxidation with BiVO 4 when considering various factors such as stability and production rates for glycerol oxidation reaction (GOR) products, surpassing the previously favored Na 2 SO 4 . Glycolaldehyde emerges as the most dominant product with ∼50% selectivity in NaNO 3 . The general applicability of our findings is confirmed by similar observation in electrochemical (EC) GOR with a polycrystalline platinum anode. Overall, these results emphasize the critical role of electrolyte selection in enhancing the efficiency of EC/PEC glycerol oxidation., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Renewable ("green") hydrogen production through direct photoelectrochemical (PEC) water splitting is a potential key contributor to the sustainable energy mix of the future. We investigate the potential of indium phosphide (InP) as a reference material among III-V semiconductors for PEC and photovoltaic (PV) applications. The p(2 × 2)/c(4 × 2)-reconstructed phosphorus-terminated p-doped InP(100) (P-rich p-InP) surface is the focus of our investigation. We employ time-resolved two-photon photoemission (tr-2PPE) spectroscopy to study electronic states near the band gap with an emphasis on normally unoccupied conduction band states that are inaccessible through conventional single-photon emission methods. The study shows the complexity of the p-InP electronic band structure and reveals the presence of at least nine distinct states between the valence band edge and vacuum energy, including a valence band state, a surface defect state pinning the Fermi level, six unoccupied surface resonances within the conduction band, as well as a cluster of states about 1.6 eV above the CBM, identified as a bulk-to-surface transition. Furthermore, we determined the decay constants of five of the conduction band states, enabling us to track electron relaxation through the bulk and surface conduction bands. This comprehensive understanding of the electron dynamics in p-InP(100) lays the foundation for further exploration and surface engineering to enhance the properties and applications of p-InP-based III-V-compounds for, e.g. , efficient and cost-effective PEC hydrogen production and highly efficient PV cells.

With the increasing pressure to decarbonize our society, green hydrogen has been identified as a key element in a future fossil fuel-free energy infrastructure. Solar water splitting through photoelectrochemical approaches is an elegant way to produce green hydrogen, but for low-value products like hydrogen, photoelectrochemical production pathways are difficult to be made economically competitive. A possible solution is to co-produce value-added chemicals. Here, we propose and demonstrate the in situ use of (photo)electrochemically generated H 2 for the homogeneous hydrogenation of itaconic acid-a biomass-derived feedstock-to methyl succinic acid. Coupling these two processes offers major advantages in terms of stability and reaction flexibility compared to direct electrochemical hydrogenation, while minimizing the overpotential. An overall conversion of up to ~60% of the produced hydrogen is demonstrated for our coupled process, and a techno-economic assessment of our proposed device further reveals the benefit of coupling solar hydrogen production to a chemical transformation., (© 2023. Springer Nature Limited.)

Hydrogen (H 2 ) produced from renewables will have a growing impact on the global energy dynamics towards sustainable and carbon-neutral standards. The share of green H 2 is still too low to meet the net-zero target, while the demand for high-quality hydrogen continues to rise. These factors amplify the need for economically viable H 2 generation technologies. The present article aims at evaluating the existing technologies for high-quality H 2 production based on solar energy. Technologies such as water electrolysis, photoelectrochemical and solar thermochemical water splitting, liquid metal reactors and plasma conversion utilize solar power directly or indirectly (as carbon-neutral electrons) and are reviewed from the perspective of their current development level, technical limitations and future potential., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Green hydrogen has been identified as a critical enabler in the global transition to sustainable energy and decarbonized society, but it is still not economically competitive compared to fossil-fuel-based hydrogen. To overcome this limitation, we propose to couple photoelectrochemical (PEC) water splitting with the hydrogenation of chemicals. Here, we evaluate the potential of co-producing hydrogen and methyl succinic acid (MSA) by coupling the hydrogenation of itaconic acid (IA) inside a PEC water splitting device. A negative net energy balance is predicted to be achieved when the device generates only hydrogen, but energy breakeven can already be achieved when a small ratio (~2%) of the generated hydrogen is used in situ for IA-to-MSA conversion. Moreover, the simulated coupled device produces MSA with much lower cumulative energy demand than conventional hydrogenation. Overall, the coupled hydrogenation concept offers an attractive approach to increase the viability of PEC water splitting while at the same time decarbonizing valuable chemical production., (© 2023. The Author(s).)

Photodeposition is a specific method for depositing metallic co-catalysts onto photocatalysts and was applied for immobilizing platinum nanoparticles onto cellulose, a photocatalytically inactive biopolymer. The obtained Pt@cellulose catalysts show narrow and well-dispersed nanoparticles with average sizes between 2 and 5 nm, whereby loading, size and distribution depend on the preparation conditions. The catalysts were investigated for the hydrogenation of para -nitrophenol via transfer hydrogenation using sodium borohydride as the hydrogen source, and the reaction rate constant was determined using the pseudo-first-order reaction rate law. The Pt@cellulose catalysts are catalytically active with rate constant values k from 0.09 × 10 -3 to 0.43 × 10 -3 min -1 , which were higher than the rate constant of a commercial Pt@Al 2 O 3 catalyst ( k = 0.09 × 10 -3 min -1 ). Additionally, the Pt@cellulose catalyst can be used for electrochemical hydrogenation of para -nitrophenol where the hydrogen is electrocatalytically formed. The electrochemical hydrogenation is faster compared to the transfer hydrogenation ( k = 0.11 min -1 )., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

When new covalent organic frameworks (COFs) are designed, the main efforts are typically focused on selecting specific building blocks with certain geometries and properties to control the structure and function of the final COFs. The nature of the linkage (imine, boroxine, vinyl, etc.) between these building blocks naturally also defines their properties. However, besides the linkage type, the orientation, i.e., the constitutional isomerism of these linkages, has rarely been considered so far as an essential aspect. In this work, three pairs of constitutionally isomeric imine-linked donor-acceptor (D-A) COFs are synthesized, which are different in the orientation of the imine bonds (D-C=N-A (DCNA) and D-N=C-A (DNCA)). The constitutional isomers show substantial differences in their photophysical properties and consequently in their photocatalytic performance. Indeed, all DCNA COFs show enhanced photocatalytic H 2 evolution performance than the corresponding DNCA COFs. Besides the imine COFs shown here, it can be concluded that the proposed concept of constitutional isomerism of linkages in COFs is quite universal and should be considered when designing and tuning the properties of COFs., (© 2022. The Author(s).)

Metal oxides are promising for photoelectrochemical (PEC) water splitting due to their robustness and low cost. However, poor charge carrier transport impedes their activity, particularly at low-bias voltage. Here we demonstrate the unusual effectiveness of phosphorus doping into bismuth vanadate (BiVO 4 ) photoanode for efficient low-bias PEC water splitting. The resulting BiVO 4 photoanode shows a separation efficiency of 80% and 99% at potentials as low as 0.6 and 1.0 V RHE , respectively. Theoretical simulation and experimental analysis collectively verify that the record performance originates from the unique phosphorus-doped BiVO 4 configuration with concurrently mediated carrier density, trap states, and small polaron hopping. With NiFeO x cocatalyst, the BiVO 4 photoanode achieves an applied bias photon-to-current efficiency of 2.21% at 0.6 V RHE . The mechanistic understanding of the enhancement of BiVO 4 properties provides key insights in trap state passivation and polaron hopping for most photoactive metal oxides., (© 2022. The Author(s).)

We present a combined computational and experimental study of the adsorption of water on the Mo-doped BiVO 4 (010) surface, revealing how excess electrons influence the dissociation of water and lead to hydroxyl-induced alterations of the surface electronic structure. By comparing ambient pressure resonant photoemission spectroscopy (AP-ResPES) measurements with the results of first-principles calculations, we show that the dissociation of water on the stoichiometric Mo-doped BiVO 4 (010) surface stabilizes the formation of a small electron polaron on the VO 4 tetrahedral site and leads to an enhanced concentration of localized electronic charge at the surface. Our calculations demonstrate that the dissociated water accounts for the enhanced V 4+ signal observed in ambient pressure X-ray photoelectron spectroscopy and the enhanced signal of a small electron polaron inter-band state observed in AP-ResPES measurements. For ternary oxide surfaces, which may contain oxygen vacancies in addition to other electron-donating dopants, our study reveals the importance of defects in altering the surface reactivity toward water and the concomitant water-induced modifications to the electronic structure.

The spatial distribution and concentration of lanthanide activator and sensitizer dopant ions are of key importance for the luminescence color and efficiency of upconverting nanoparticles (UCNPs). Quantifying dopant ion distributions and intermixing, and correlating them with synthesis methods require suitable analytical techniques. Here, X-ray photoelectron spectroscopy depth-profiling with tender X-rays (2000-6000 eV), providing probe depths ideally matched to UCNP sizes, is used to measure the depth-dependent concentration ratios of Er 3+ to Yb 3+ , [Er 3+ ]/[Yb 3+ ], in three types of UCNPs prepared using different reagents and synthesis methods. This is combined with data simulations and inductively coupled plasma-optical emission spectroscopy (ICP-OES) measurements of the lanthanide ion concentrations to construct models of the UCNPs' dopant ion distributions. The UCNP sizes and architectures are chosen to demonstrate the potential of this approach. Core-only UCNPs synthesized with XCl 3 ·6H 2 O precursors (β-phase) exhibit a homogeneous distribution of lanthanide ions, but a slightly surface-enhanced [Er 3+ ]/[Yb 3+ ] is observed for UCNPs prepared with trifluroacetate precursors (α-phase). Examination of Yb-core@Er-shell UCNPs reveals a co-doped, intermixed region between the single-doped core and shell. The impact of these different dopant ion distributions on the UCNP's optical properties is discussed to highlight their importance for UCNP functionality and the design of efficient UCNPs., (© 2022 The Authors. Small published by Wiley-VCH GmbH.)

The semiconductor-liquid junction (SCLJ), the dominant place in photoelectrochemical (PEC) catalysis, determines the interfacial activity and stability of photoelectrodes, whcih directly affects the viability of PEC hydrogen generation. Though efforts dedicated in past decades, a challenge remains regarding creating a synchronously active and stable SCLJ, owing to the technical hurdles of simultaneously overlaying the two advantages. The present work demonstrates that creating an SCLJ with a unique configuration of the dual interfacial layers can yield BiVO 4 photoanodes with synchronously boosted photoelectrochemical activity and operational stability, with values located at the top in the records of such photoelectrodes. The bespoke dual interfacial layers, accessed via grafting laser-generated carbon dots with phenolic hydroxyl groups (LGCDs-PHGs), are experimentally verified effective, not only in generating the uniform layer of LGCDs with covalent anchoring for inhibited photocorrosion, but also in activating, respectively, the charge separation and transfer in each layer for boosted charge-carrier kinetics, resulting in FeNiOOH-LGCDs-PHGs-MBVO photoanodes with a dual configuration with the photocurrent density of 6.08 mA cm -2 @ 1.23 V RHE , and operational stability up to 120 h @ 1.23 V RHE . Further work exploring LGCDs-PHGs from catecholic molecules warrants the proposed strategy as being a universal alternative for addressing the interfacial charge-carrier kinetics and operational stability of semiconductor photoelectrodes., (© 2022 Wiley-VCH GmbH.)

A previously developed sustainable immobilization concept for photocatalysts based on cellulose as a renewable support material was applied for the photocatalytic hydrogenation of acetophenone (ACP) to 1-phenyl ethanol (PE). Four different TiO 2 modifications (P25, P90, PC105, and PC500) were screened for the reaction showing good performance for PC25 and PC500. PC500 was selected for a detailed kinetic study to find the optimal operating conditions, and to obtain a better understanding of the photocatalytic pathway in relation to conventional and transfer hydrogenation. The kinetic data were analyzed using the pseudo-first-order reaction rate law. A complete conversion was obtained for ACP concentrations below 1 mM using a 360 nm filter and argon as the purge gas within 2-3 hours. High oxygen concentrations slow down or prevent the reaction, and wavelengths below 300 nm lead to side-products. By investigating the temperature dependency, an activation energy of 22 kJ mol -1 was determined which is lower than the activation energies for conventional and transfer hydrogenation, because the light activation of the photocatalyst turns the endothermic to an exothermic reaction. PC500 was immobilized onto the cellulose film showing a 37% lower activity that remains almost constant after multiple use., Competing Interests: The authors declare no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

Covalent organic frameworks (COFs) have emerged as an important class of organic semiconductors and photocatalysts for the hydrogen evolution reaction (HER)from water. To optimize their photocatalytic activity, typically the organic moieties constituting the frameworks are considered and the most suitable combinations of them are searched for. However, the effect of the covalent linkage between these moieties on the photocatalytic performance has rarely been studied. Herein, we demonstrate that donor-acceptor (D-A) type imine-linked COFs can produce hydrogen with a rate as high as 20.7 mmol g -1  h -1 under visible light irradiation, upon protonation of their imine linkages. A significant red-shift in light absorbance, largely improved charge separation efficiency, and an increase in hydrophilicity triggered by protonation of the Schiff-base moieties in the imine-linked COFs, are responsible for the improved photocatalytic performance., (© 2021 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Light absorption in strongly correlated electron materials can excite electrons and holes into a variety of different states. Some of these excitations yield mobile charge carriers, whereas others result in localized states that cannot contribute to photocurrent. The photogeneration yield spectrum, ξ(λ), represents the wavelength-dependent ratio between the contributing absorption that ultimately generates mobile charge carriers and the overall absorption. Despite being a vital material property, it is not trivial to characterize. Here, we present an empirical method to extract ξ(λ) through optical and external quantum efficiency measurements of ultrathin films. We applied this method to haematite photoanodes for water photo-oxidation, and observed that it is self-consistent for different illumination conditions and applied potentials. We found agreement between the extracted ξ(λ) spectrum and the photoconductivity spectrum measured by time-resolved microwave conductivity. These measurements revealed that mobile charge carrier generation increases with increasing energy across haematite's absorption spectrum. Low-energy non-contributing absorption fundamentally limits the photoconversion efficiency of haematite photoanodes and provides an upper limit to the achievable photocurrent that is substantially lower than that predicted based solely on absorption above the bandgap. We extended our analysis to TiO 2 and BiVO 4 photoanodes, demonstrating the broader utility of the method for determining ξ(λ).

There is an urgent need for cheap, stable, and abundant catalyst materials for photoelectrochemical water splitting. Manganese oxide is an interesting candidate as an oxygen evolution reaction (OER) catalyst, but the minimum thickness above which MnO x thin films become OER-active has not yet been established. In this work, ultrathin (<10 nm) manganese oxide films are grown on silicon by atomic layer deposition to study the origin of OER activity under alkaline conditions. We found that MnO x films thinner than 1.5 nm are not OER-active. X-ray photoelectron spectroscopy shows that this is due to electrostatic catalyst-support interactions that prevent the electrochemical oxidation of the manganese ions close to the interface with the support, while in thicker films, Mn III and Mn IV oxide layers appear as OER-active catalysts after oxidation and electrochemical treatment. From our investigations, it can be concluded that one Mn III,IV -O monolayer is sufficient to establish oxygen evolution under alkaline conditions. The results of this study provide important new design criteria for ultrathin manganese oxide oxygen evolution catalysts.

Photoelectrochemical water splitting is a promising route to produce hydrogen from solar energy. However, corrosion of photoelectrodes remains a fundamental challenge for their implementation. Here, we reveal different dissolution behaviors of BiVO 4 photoanode in pH-buffered borate, phosphate, and citrate (hole-scavenger) electrolytes, studied in operando employing an illuminated scanning flow cell. We demonstrate that decrease in photocurrents alone does not reflect the degradation of photoelectrodes. Changes in dissolution rates correlate to the evolution of surface chemistry and morphology. The correlative measurements on both sides of the liquid-semiconductor junction provide quantitative comparison and mechanistic insights into the degradation processes., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)