Selective Control and Characteristics of Water Oxidation and Dioxygen Reduction in Environmental Photo(electro)catalytic Systems.

ConspectusEmploying semiconductor materials is a popular engineering method to harvest solar energy, which is widely investigated for photocatalysis (PC) and photoelectrocatalysis (PEC) that convert solar light to chemical energy. In particular, environmental photo(electro)catalysis has been extensively studied as a sustainable method for water treatment, air purification, and resource recovery. Environmental PC/PEC processes working in ambient conditions are initiated mainly through hole transfer to water (water oxidation) and electron transfer to dioxygen (O2 reduction) and the subsequent photoredox transformation of water and dioxygen serves as a base of various PC/PEC systems. Through the redox transformations, different products can be generated depending on the number of transferred electrons and holes. The single electron/hole transfer generates radical species and reactive oxygen species (ROS) which initiate the degradation/transformation of various pollutants in water and air, while the multicharge transfer can generate energy-rich chemicals (e.g., H2, H2O2). Therefore, understanding the characteristics of the photoredox reactions of water and dioxygen on the semiconductor surface is critically important in controlling the selectivity and efficiency of photoconversion processes.In this Account, we describe various environmental PC/PEC conversions with a particular focus on how the phototransformation of dioxygen and water is related to the overall processes occurring on diverse semiconductor materials. The activation of water or dioxygen can be controlled by modifying the properties of semiconductors, changing the kind of counterpart half-reaction and the experimental conditions. If water can be used as a ubiquitous reductant under solar irradiation, many kinds of reductive transformations can be carried out under ambient environmental conditions. For example, various toxic oxyanions (or metal ions) can be reductively transformed to harmless or less harmful species or useful chemicals/fuels can be synthesized under ambient conditions if water can provide electrons and protons via solar water oxidation. On the other hand, dioxygen can turn into reactive oxygen species (ROS) as a versatile oxidant or to a chemical like H2O2. There should be many more possibilities of utilizing the photoconversion of water and dioxygen for environmentally significant purposes, which are yet to be further developed and demonstrated. In this Account, we highlight the recent strategies and the novel functional materials for effective activation of water and dioxygen in environmental PC/PEC systems. Design of environmentally functional PC/PEC systems should be based on better understanding of water and dioxygen activation.

Sculpting In-plane Fractal Porous Patterns in Two-Dimensional MOF Nanocrystals for Photoelectrocatalytic CO2 Reduction.

Herein, by choosing few-nm-thin two-dimensional (2D) nanocrystals of MOF-5 containing in-planner square lattices as a modular platform, a crystal lattice-guided wet-chemical etching has been rationally accomplished. As a result, two attractive pore patterns carrying Euclidean curvatures; precisely, plus(+)-shaped and fractal-patterned pores via ⟨100⟩ and ⟨110⟩ directional etching, respectively, are regulated in contrast to habitually formed spherical-shaped random etches on MOF surface. In agreement with the theoretical calculations, a diffusion-limited etching process has been optimized to devise high-yield of size-tunable fractal-pores on the MOF surface that tenders for a compatibly high payload of catalytic ReI -complexes using the existing large edge area once modified into a free amine-group-exposed inner pore surface. Finally, on benefiting from the long-range fractal opening in 2D MOF support structure, while loaded on an electrode surface, a facilitated cross-interface charge-transportation and well-exposure of immobilized ReI -catalysts are anticipated, thus realizing enhanced activity and stability of the supported catalyst in photoelectrochemical CO2 -to-CO reduction.

Integrated electrocatalytic synthesis of ammonium nitrate from dilute NO gas on metal organic frameworks-modified gas diffusion electrodes.

The electrocatalytic conversion of NO offers a promising technology for not only removing the air pollutant but also synthesizing valuable chemicals. We design an integrated-electrocatalysis cell featuring metal organic framework (MOF)-modified gas diffusion electrodes for simultaneous capture of NO and generation of NH4NO3 under low-concentration NO flow conditions. Using 2% NO gas, the modified cathode exhibits a higher NH4+ yield and Faradaic efficiency than an unmodified cathode. Notably, the modified cathode shows a twofold increase in NH4+ production with 20 ppm NO gas supply. Theoretical calculations predict favorable transfer of adsorbed NO from the adsorption layer to the catalyst layer, which is experimentally confirmed by enhanced NO mass transfer from gas to electrolyte across the modified electrode. The adsorption layer-modified anode also exhibits a higher NO3- yield for NO electro-oxidation compared to the unmodified electrode under low NO concentration flow. Among various integrated-cell configurations, a single-chamber setup produces a higher NH4NO3 yield than a double-chamber setup. Furthermore, a higher NO utilization efficiency is obtained with a single-gasline operation mode, where the NO-containing gas flows sequentially from the cathode to the anode.

Diabetes Fact Sheets in Korea, 2020: An Appraisal of Current Status.

BACKGROUND: This study aimed to investigate the recent prevalence, management, and comorbidities of diabetes among Korean adults aged ≥30 years by analyzing nationally representative data. METHODS: This study used data from the Korea National Health and Nutrition Examination Survey from 2016 to 2018, and the percentage and total number of people ≥30 years of age with diabetes and impaired fasting glucose (IFG) were estimated. RESULTS: In 2018, 13.8% of Korean adults aged ≥30 years had diabetes, and adults aged ≥65 years showed a prevalence rate of 28%. The prevalence of IFG was 26.9% in adults aged ≥30 years. From 2016 to 2018, 35% of the subjects with diabetes were not aware of their condition. Regarding comorbidities, 53.2% and 61.3% were obese and hypertensive, respectively, and 72% had hypercholesterolemia as defined by low-density lipoprotein cholesterol (LDL-C) ≥100 mg/dL in people with diabetes. Of the subjects with diabetes, 43.7% had both hypertension and hypercholesterolemia. With regard to glycemic control, only 28.3% reached the target level of <6.5%. Moreover, only 11.5% of subjects with diabetes met all three targets of glycosylated hemoglobin, blood pressure, and LDL-C. The percentage of energy intake from carbohydrates was higher in diabetes patients than in those without diabetes, while that from protein and fat was lower in subjects with diabetes. CONCLUSION: The high prevalence and low control rate of diabetes and its comorbidities in Korean adults were confirmed. More stringent efforts are needed to improve the comprehensive management of diabetes to reduce diabetes-related morbidity and mortality.

Holey Pt Nanosheets on NiFe-Hydroxide Laminates: Synergistically Enhanced Electrocatalytic 2D Interface toward Hydrogen Evolution Reaction.

Next-generation electrocatalysts with smart integrated designs, maximizing the chemical cascade synergy for sustainable hydrogen production, are needed to address the urgent environmental threats, but scalable synthesis of precisely architectured nanohybrids rendering a few-nanometer interfacial controllability to augment the catalytic reactivity and operational stability is a major bottleneck. Herein, by inventing a surface-confined lateral growth of nanometer-thin and nanoporous two-dimensional (2D)-Pt on NiFe-LDH nanosheets, a highly reactive 2D-2D interfacially integrated nanoplatform is synthesized for an alkaline hydrogen evolution reaction (HER) which not only extracts high Pt-atomic utilization efficiency but also synergistically accelerates the water dissociation and hydrogen generation cascade on the colocalized Pt/M(OH)x active sites, endowing a 6.1-fold higher Pt mass activity than 20% Pt/C and also empowers a record-high HER operational stability for 50 h, due to the chemically enforced lamellar architecture. This work offers a gateway to produce active metal nanosheets tailored with a suitable active-template surface in order to invent and enforce futuristic catalysis technologies.