Unassisted Photoelectrochemical H2O2 Production with In Situ Glycerol Valorization Using α-Fe2O3.

Photoelectrochemical (PEC) H2O2 production via two-electron O2 reduction is promising for H2O2 production without emitting CO2. For PEC H2O2 production, α-Fe2O3 is an ideal semiconductor owing to its earth abundance, superior stability in water, and an appropriate band gap for efficient solar light utilization. Moreover, its conduction band is suitable for O2 reduction to produce H2O2. However, a significant overpotential for water oxidation is required due to the poor surface properties of α-Fe2O3. Thus, unassisted solar H2O2 production is not yet possible. Herein, we demonstrate unassisted PEC H2O2 production using α-Fe2O3 for the first time by applying glycerol oxidation, which requires less bias compared with water oxidation. We obtain maximum Faradaic efficiencies of 96.89 ± 0.6% and 100% for glycerol oxidation and H2O2 production, respectively, with high stability for 25 h. Our results indicate that unassisted and stable PEC H2O2 production is feasible with in situ glycerol valorization using the α-Fe2O3 photoanode.

Homogeneously Mixed Cu-Co Bimetallic Catalyst Derived from Hydroxy Double Salt for Industrial-Level High-Rate Nitrate-to-Ammonia Electrosynthesis.

Electrocatalytic nitrate reduction reaction (NO3RR) presents an innovative approach for sustainable NH3 production. However, selective NH3 production is hindered by the multiple intermediates involved in the NO3RR process and the competitive hydrogen evolution reaction. Hence, the development of highly efficient NO3RR catalysts is paramount. Herein, we report highly efficient bimetallic catalysts derived from hydroxy double salt (HDS). Under NO3RR conditions, Cu1Co1-HDS undergoes in situ reconstruction, forming nanocomposites of homogeneously distributed metallic Cu0 and Co(OH)2. Reconstruction-induced Cu0 rapidly converts NO3- to NO2-, which is further hydrogenated to NH3 by Co(OH)2. Homogeneously mixed Cu and Co species maximize this synergistic effect, achieving outstanding NO3RR performance including the highest NH3 yield rate (4.625 mmol h-1 cm-2) reported for powder-type NO3RR catalysts. Integration of Cu1Co1-HDS with a commercial Si solar cell attained 4.53% solar-to-ammonia efficiency from industrial wastewater-level concentrations of NO3- (2000 ppm), demonstrating practical application potential for solar-driven NH3 production. This study provides a strategy for enhancing the NH3 yield rate by optimizing the compositions and distributions of Cu and Co.

High-Performance Electrochemical and Photoelectrochemical Water Splitting at Neutral pH by Ir Nanocluster-Anchored CoFe-Layered Double Hydroxide Nanosheets.

Highly efficient electrocatalysts for the oxygen evolution reaction (OER) in neutral electrolytes are indispensable for practical electrochemical and photoelectrochemical water splitting technologies. However, there is a lack of good, neutral OER electrocatalysts because of the poor stability when H+ accumulates during the OER and slow OER kinetics at neutral pH. Herein, we report Ir species nanocluster-anchored, Co/Fe-layered double hydroxide (LDH) nanostructures in which the crystalline nature of LDH-restrained corrosion associated with H+ and the Ir species dramatically enhanced the OEC kinetics at neutral pH. The optimized OER electrocatalyst demonstrated a low overpotential of 323 mV (at 10 mA cm-2) and a record low Tafel slope of 42.8 mV dec-1. When it was integrated with an organic semiconductor-based photoanode, we obtained a photocurrent density of 15.2 mA cm-2 at 1.23 V versus reversible hydrogen in neutral electrolyte, which is the highest among all reported photoanodes to our knowledge.

Hydrogeological characteristics and water chemistry in a coastal aquifer of Korea: implications for land subsidence.

Land subsidence is the gradual or sudden dropping of the ground surface developed by increasing the total stress. Most studies have discussed the relationship between land subsidence with groundwater level. However, there is a lack of discussion on groundwater environmental changes after occurring land subsidence. This study aimed to evaluate the hydrogeological and water chemistry characteristics of construction sites with land subsidence. Land subsidence in the Yangyang coastal area occurred suddenly on August 3, 2022, when the retaining wall of the construction collapsed. The groundwater level was measured three times, and water samples were collected twice between August 5, 2022, and September 5, 2022, for laboratory analysis. After land subsidence occurred, the average groundwater level was - 19.91 m ground level (GL) on August 9, 2022, and finally decreased to - 19.21 m GL on September 05, 2022. The groundwater levels surrounding the construction site gradually increased for a month. The electrical conductivity value measured at the monitoring wells ranged from 89 to 7800 µS/cm, and four wells exceeded the measurement limit near the groundwater leaked points. The highest mixing ratio of leaked water samples, collected on August 9, 2022, was 27.6%. Furthermore, the fresh groundwater-saltwater interface depth was estimated to be above the construction bottom. Although groundwater levels recovered, the groundwater quality continuously is affected by saltwater. This finding could contribute to understanding the hydrogeological characteristics surrounding construction sites with land subsidence and provide insight into the hydrochemical evolution process during declined groundwater levels in coastal aquifers.

Cyber loss model risk translates to premium mispricing and risk sensitivity.

In this paper we focus on model risk and risk sensitivity when addressing the insurability of cyber risk. The standard statistical approaches to assessment of insurability and potential mispricing are enhanced in several aspects involving consideration of model risk. Model risk can arise from model uncertainty and parameter uncertainty. We demonstrate how to quantify the effect of model risk in this analysis by incorporating various robust estimators for key model parameters that apply in both marginal and joint cyber risk loss process modelling. Through this analysis we are able to address the question that, to the best of our knowledge, no other study has investigated in the context of cyber risk: is model risk present in cyber risk data, and how does is it translate into premium mispricing? We believe our findings should complement existing studies seeking to explore the insurability of cyber losses.

Toward practical solar hydrogen production - an artificial photosynthetic leaf-to-farm challenge.

Solar water splitting is a promising approach to transform sunlight into renewable, sustainable and green hydrogen energy. There are three representative ways of transforming solar radiation into molecular hydrogen, which are the photocatalytic (PC), photoelectrochemical (PEC), and photovoltaic-electrolysis (PV-EC) routes. Having the future perspective of green hydrogen economy in mind, this review article discusses devices and systems for solar-to-hydrogen production including comparison of the above solar water splitting systems. The focus is placed on a critical assessment of the key components needed to scale up PEC water splitting systems such as materials efficiency, cost, elemental abundancy, stability, fuel separation, device operability, cell architecture, and techno-economic aspects of the systems. The review follows a stepwise approach and provides (i) a summary of the basic principles and photocatalytic materials employed for PEC water splitting, (ii) an extensive discussion of technologies, procedures, and system designs, and (iii) an introduction to international demonstration projects, and the development of benchmarked devices and large-scale prototype systems. The task of scaling up of laboratory overall water splitting devices to practical systems may be called "an artificial photosynthetic leaf-to-farm challenge".

Aqueous-solution route to zinc telluride films for application to CO2 reduction.

As a photocathode for CO2 reduction, zinc-blende zinc telluride (ZnTe) was directly formed on a Zn/ZnO nanowire substrate by a simple dissolution-recrystallization mechanism without any surfactant. With the most negative conduction-band edge among p-type semiconductors, this new photocatalyst showed efficient and stable CO formation in photoelectrochemical CO2 reduction at -0.2--0.7 V versus RHE without a sacrificial reagent.

Artificial Intelligence-Assisted Daily Quality Control System for the Histologic Diagnosis of Gastrointestinal Endoscopic Biopsies: A 1-Year Experience.

CONTEXT.­: Seegene Medical Foundation, one of the major clinical laboratories in South Korea, developed SeeDP, an artificial intelligence (AI)-based postanalytic daily quality control (QC) system that reassesses all gastrointestinal (GI) endoscopic biopsy (EB) slides for incorrect diagnoses. OBJECTIVE.­: To review the operational records and clinical impact of SeeDP since its launch in March 2022. DESIGN.­: Operational records of SeeDP were retrieved for the period of March 1, 2022, to February 28, 2023. Among cases scanned during 40 working days (March 10, 2022, to May 4, 2022), all discordant cases encountered by 2 pathologists were reviewed. Cases of SeeDP-assisted revised diagnoses were collected and compared with cases recognized using conventional methods. RESULTS.­: Occasional scanner failures and various types of aberrant errors compromised QC coverage, resulting in the scanning of only 67.7% (572 254 of 844 906) of all EB slides submitted and 0.8% of the scanned slides being further excluded from the AI analysis. The AI predictions differed from the pathologists' diagnoses in 42 760 of the 557 672 gastrointestinal EB slides (7.7%) successfully assessed by the AI models; however, a detailed review of discordant slides revealed that true misdiagnosis accounted for only 5.5% (25 of 454) of the disagreements. Compared with conventional error recognition methods, SeeDP detected more misdiagnoses (7 versus 14) within a significantly shorter time (average, 3.6 versus 38.7 days; P < .001), including 1 signet ring cell carcinoma initially diagnosed as gastritis. CONCLUSIONS.­: AI-based daily QC systems are plausible solutions to guarantee high-quality pathologic diagnosis by enabling rapid detection and correction of misdiagnosis.

Understanding the preparative chemistry of atomically dispersed nickel catalysts for achieving high-efficiency H2O2 electrosynthesis.

Electrochemical hydrogen peroxide (H2O2) production via two-electron oxygen reduction reaction (2e- ORR) has received increasing attention as it enables clean, sustainable, and on-site H2O2 production. Mimicking the active site structure of H2O2 production enzymes, such as nickel superoxide dismutase, is the most intuitive way to design efficient 2e- ORR electrocatalysts. However, Ni-based catalysts have thus far shown relatively low 2e- ORR activity. In this work, we present the design of high-performing, atomically dispersed Ni-based catalysts (Ni ADCs) for H2O2 production through understanding the formation chemistry of the Ni-based active sites. The use of a precoordinated precursor and pyrolysis within a confined nanospace were found to be essential for generating active Ni-N x sites in high density and increasing carbon yields, respectively. A series of model catalysts prepared from coordinating solvents having different vapor pressures gave rise to Ni ADCs with controlled ratios of Ni-N x sites and Ni nanoparticles, which revealed that the Ni-N x sites have greater 2e- ORR activity. Another set of Ni ADCs identified the important role of the degree of distortion from the square planar structure in H2O2 electrosynthesis activity. The optimized catalyst exhibited a record H2O2 electrosynthesis mass activity with excellent H2O2 selectivity.

Fabrication of CaFe2O4/TaON heterojunction photoanode for photoelectrochemical water oxidation.

Tantalum oxynitride photoanode is fabricated and modified with calcium ferrite to form a heterojunction anode for a photoelectrochemical water splitting cell. The synthesized powders are loaded sequentially to the transparent conducting glass by electrophoretic deposition, which is advantageous to form a uniform layer and a junction structure. X-ray diffraction, UV-vis diffuse reflectance spectroscopy, scanning electron microscopy, and impedance spectroscopy analysis are conducted to investigate the structural, morphological, and electrochemical characteristics of the anode. The introduction of CaFe2O4 overlayer onto TaON electrode increases the photocurrent density about five times at 1.23 V vs reversible hydrogen electrode without any co-catalyst. Impedance spectroscopy analysis indicates that the junction formation increased photocurrent density by reducing the resistance to the transport of charge carriers and thereby enhancing the electron-hole separation. This photocurrent generation is a result of the overall water splitting as confirmed by evolution of hydrogen and oxygen in a stoichiometric ratio. From the study of different junction configurations, it is established that the intimate contact between TaON and CaFe2O4 is critical for enhanced performance of the heterojunction anode for photoelectrochemical water oxidation under simulated sun light.

Self-assembled gold nanoparticle-mixed metal oxide nanocomposites for self-sensitized dye degradation under visible light irradiation.

Gold nanoparticle (Au NP)-mixed metal oxide (MMO) nanocomposite photocatalysts for efficient self-sensitized dye degradations under visible light were prepared by an electrostatically driven self-assembly. Dihydrolipoic acid (DHLA)-capped Au NPs (building block I) were synthesized through a room temperature reaction. Their hydrodynamic size was determined as being around 4.9 nm by dynamic light scattering measurements. MMO nanoplates with lateral dimensions of 100-250 nm (building block II) were prepared by a calcination of zinc aluminum layered double hydroxides at 750 °C for 2 h in air. In a pH 7.0 aqueous solution, the DHLA-capped Au NPs had a negative zeta potential (-22 ± 3 mV); on the other hand, the MMO nanoplates had a positive zeta potential (15 ± 2 mV). Electrostatic self-assembly was achieved by stirring an aqueous solution (pH 7.0) containing DHLA-capped Au NPs and MMO nanoplates at room temperature for 1 h. The self-assembled and sequentially calcined nanocomposites exhibited the superior self-sensitized dye degradation efficiency under visible light to that of ZnO, TiO(2) (P25), or pure MMO nanoplates. The enhanced degradation efficiency could be attributed to strong coupling interactions of ZnO and ZnAl(2)O(4) phases of the MMO and the role of Au as an electron sink and mediator for formations of reactive oxidation species and as a light concentrator.

Bias-free solar hydrogen production at 19.8 mA cm-2 using perovskite photocathode and lignocellulosic biomass.

Solar hydrogen production is one of the ultimate technologies needed to realize a carbon-neutral, sustainable society. However, an energy-intensive water oxidation half-reaction together with the poor performance of conventional inorganic photocatalysts have been big hurdles for practical solar hydrogen production. Here we present a photoelectrochemical cell with a record high photocurrent density of 19.8 mA cm-2 for hydrogen production by utilizing a high-performance organic-inorganic halide perovskite as a panchromatic absorber and lignocellulosic biomass as an alternative source of electrons working at lower potentials. In addition, value-added chemicals such as vanillin and acetovanillone are produced via the selective depolymerization of lignin in lignocellulosic biomass while cellulose remains close to intact for further utilization. This study paves the way to improve solar hydrogen productivity and simultaneously realize the effective use of lignocellulosic biomass.

Improving quality control in the routine practice for histopathological interpretation of gastrointestinal endoscopic biopsies using artificial intelligence.

BACKGROUND: Colorectal and gastric cancer are major causes of cancer-related deaths. In Korea, gastrointestinal (GI) endoscopic biopsy specimens account for a high percentage of histopathologic examinations. Lack of a sufficient pathologist workforce can cause an increase in human errors, threatening patient safety. Therefore, we developed a digital pathology total solution combining artificial intelligence (AI) classifier models and pathology laboratory information system for GI endoscopic biopsy specimens to establish a post-analytic daily fast quality control (QC) system, which was applied in clinical practice for a 3-month trial run by four pathologists. METHODS AND FINDINGS: Our whole slide image (WSI) classification framework comprised patch-generator, patch-level classifier, and WSI-level classifier. The classifiers were both based on DenseNet (Dense Convolutional Network). In laboratory tests, the WSI classifier achieved accuracy rates of 95.8% and 96.0% in classifying histopathological WSIs of colorectal and gastric endoscopic biopsy specimens, respectively, into three classes (Negative for dysplasia, Dysplasia, and Malignant). Classification by pathologic diagnosis and AI prediction were compared and daily reviews were conducted, focusing on discordant cases for early detection of potential human errors by the pathologists, allowing immediate correction, before the pathology report error is conveyed to the patients. During the 3-month AI-assisted daily QC trial run period, approximately 7-10 times the number of slides compared to that in the conventional monthly QC (33 months) were reviewed by pathologists; nearly 100% of GI endoscopy biopsy slides were double-checked by the AI models. Further, approximately 17-30 times the number of potential human errors were detected within an average of 1.2 days. CONCLUSIONS: The AI-assisted daily QC system that we developed and established demonstrated notable improvements in QC, in quantitative, qualitative, and time utility aspects. Ultimately, we developed an independent AI-assisted post-analytic daily fast QC system that was clinically applicable and influential, which could enhance patient safety.

Three-dimensional type II ZnO/ZnSe heterostructures and their visible light photocatalytic activities.

We report a method for synthesizing three distinct type II 3D ZnO/ZnSe heterostructures through simple solution-based surface modification reactions in which polycrystalline ZnSe nanoparticles formed on the surfaces of single-crystalline ZnO building blocks of 3D superstructures. The experimental results suggested a possible formation mechanism for these heterostructures. The formation of the ZnO/ZnSe heterostructures was assumed to result from a dissolution-recrystallization mechanism. The optical properties of the 3D ZnO/ZnSe heterostructures were probed by UV-vis diffuse reflectance spectroscopy. The 3D ZnO/ZnSe heterostructures exhibited absorption in the visible spectral region. The visible photocatalytic activities of 3D ZnO/ZnSe heterostructures were much higher than those of the 3D pure ZnO structures. The activities of the 3D ZnO/ZnSe heterostructures varied according to the structures under visible light. The morphologies and exposed crystal faces of pure ZnO building blocks prior to surface modification had a significant effect on the visible light photocatalytic processes of ZnO/ZnSe heterostructures after surface modification.

Formation of amorphous zinc citrate spheres and their conversion to crystalline ZnO nanostructures.

We report a method for synthesizing zinc citrate spheres at a low temperature (90 °C) under normal atmospheric pressure. The spherical structures were amorphous and had an average diameter of ∼1.7 µm. The amorphous zinc citrate spheres could be converted into crystalline ZnO nanostructures in aqueous solutions by heating at 90 °C for 1 h. By local dissolution of the zinc citrate spheres, nucleation and growth of ZnO occurred on the surfaces of the amorphous zinc citrate spheres. The morphologies and exposed crystal faces of the crystalline ZnO nanostructures (structure I: oblate spheroid; structure II: prolate spheroid; structure III: hexagonal disk; structure IV: sphere) could be controlled simply by varying the solution composition (solutions I, II, III, or IV) in which the as-prepared amorphous zinc citrate spheres were converted. The concentration of citrate anions and solution pH played a decisive role in determining the morphologies and exposed crystal faces of the crystalline ZnO nanostructures. On the basis of experimental results, we propose a plausible mechanism for the conversion of amorphous zinc citrate spheres into the variety of observed ZnO structures.

Unassisted selective solar hydrogen peroxide production by an oxidised buckypaper-integrated perovskite photocathode.

Hydrogen peroxide (H2O2) is an eco-friendly oxidant and a promising energy source possessing comparable energy density to that of compressed H2. The current H2O2 production strategies mostly depend on the anthraquinone oxidation process, which requires significant energy and numerous organic chemicals. Photocatalyst-based solar H2O2 production comprises single-step O2 reduction to H2O2, which is a simple and eco-friendly method. However, the solar-to-H2O2 conversion efficiency is limited by the low performance of the inorganic semiconductor-based photoelectrodes and low selectivity and stability of the H2O2 production electrocatalyst. Herein, we demonstrate unassisted solar H2O2 production using an oxidised buckypaper as the H2O2 electrocatalyst combined with a high-performance inorganic-organic hybrid (perovskite) photocathode, without the need for additional bias or sacrificial agents. This integrated photoelectrode system shows 100% selectivity toward H2O2 and a solar-to-chemical conversion efficiency of ~1.463%.

Alkali-Metal-Mediated Reversible Chemical Hydrogen Storage Using Seawater.

The economic viability and systemic sustainability of a green hydrogen economy are primarily dependent on its storage. However, none of the current hydrogen storage methods meet all the targets set by the US Department of Energy (DoE) for mobile hydrogen storage. One of the most promising routes is through the chemical reaction of alkali metals with water; however, this method has not received much attention owing to its irreversible nature. Herein, we present a reconditioned seawater battery-assisted hydrogen storage system that can provide a solution to the irreversible nature of alkali-metal-based hydrogen storage. We show that this system can also be applied to relatively lighter alkali metals such as lithium as well as sodium, which increases the possibility of fulfilling the DoE target. Furthermore, we found that small (1.75 cm2) and scaled-up (70 cm2) systems showed high Faradaic efficiencies of over 94%, even in the presence of oxygen, which enhances their viability.

Exposed crystal face controlled synthesis of 3D ZnO superstructures.

We report a method for synthesizing exposed crystal face controlled 3D ZnO superstructures under mild conditions (at room temperature or 90 degrees C under 1 atm) without organic additives. The exposed crystal faces of the building blocks of the 3D structures were controlled by varying the reactant concentrations and the reaction temperatures. On the basis of the experimental results, we speculated a possible mechanism for the formation of the four distinct 3D ZnO superstructures (structures I, II, III, and IV) under the different growth conditions. The optical properties of the 3D ZnO superstructures were probed by UV-vis diffuse reflectance spectroscopy. The spectra were shifted depending on the dimensions and sizes of the building blocks of the 3D superstructures. The photocatalytic activities of the 3D superstructures varied according to the exposed crystal faces, which could be controlled by this method (structure I > structure IV > structure III > structure II).

Superaerophobic hydrogels for enhanced electrochemical and photoelectrochemical hydrogen production.

The efficient removal of gas bubbles in (photo)electrochemical gas evolution reactions is an important but underexplored issue. Conventionally, researchers have attempted to impart bubble-repellent properties (so-called superaerophobicity) to electrodes by controlling their microstructures. However, conventional approaches have limitations, as they are material specific, difficult to scale up, possibly detrimental to the electrodes' catalytic activity and stability, and incompatible with photoelectrochemical applications. To address these issues, we report a simple strategy for the realization of superaerophobic (photo)electrodes via the deposition of hydrogels on a desired electrode surface. For a proof-of-concept demonstration, we deposited a transparent hydrogel assembled from M13 virus onto (photo)electrodes for a hydrogen evolution reaction. The hydrogel overlayer facilitated the elimination of hydrogen bubbles and substantially improved the (photo)electrodes' performances by maintaining high catalytic activity and minimizing the concentration overpotential. This study can contribute to the practical application of various types of (photo)electrochemical gas evolution reactions.

High-performance and stable photoelectrochemical water splitting cell with organic-photoactive-layer-based photoanode.

Considering their superior charge-transfer characteristics, easy tenability of energy levels, and low production cost, organic semiconductors are ideal for photoelectrochemical (PEC) hydrogen production. However, organic-semiconductor-based photoelectrodes have not been extensively explored for PEC water-splitting because of their low stability in water. Herein, we report high-performance and stable organic-semiconductors photoanodes consisting of p-type polymers and n-type non-fullerene materials, which is passivated using nickel foils, GaIn eutectic, and layered double hydroxides as model materials. We achieve a photocurrent density of 15.1 mA cm-2 at 1.23 V vs. reversible hydrogen electrode (RHE) with an onset potential of 0.55 V vs. RHE and a record high half-cell solar-to-hydrogen conversion efficiency of 4.33% under AM 1.5 G solar simulated light. After conducting the stability test at 1.3 V vs. RHE for 10 h, 90% of the initial photocurrent density are retained, whereas the photoactive layer without passivation lost its activity within a few minutes.