Organic molecules as mediators and catalysts for photocatalytic and electrocatalytic CO2 reduction

Reduction of CO2 by electrochemical and photoelectrochemical methods to produce carbon-rich fuels is a heavily pursued research theme. Most of the current efforts are focused on the development of transition-metal-based catalysts. In this tutorial review, we present an overview of the development of organic molecules as mediators and catalysts for CO2 reduction. Four classes of organic molecules are discussed: tetraalkylammonium salts, aromatic esters and nitriles, ionic liquids, and pyridinium derivatives. It is shown that reactions mediated or catalyzed by these organic molecules can be competitive compared to their metal-catalyzed counterparts, both in terms of product selectivity and energy efficiency

Electrochemical reduction of CO2 in organic solvents catalyzed by MoO2

MoO2 microparticles act as an active catalyst for the electrochemical reduction of CO2 in organic solvents such as acetonitrile and dimethylformamide. The catalytic activity and product selectivity depend on temperature and water content of the solvent

Electrochemical Reduction of CO2 Catalyzed by Metal Oxides

A rapidly growing population and industrialization have caused the exploitation of natural resources in keeping with fossil fuels shortage. Due to the combustion of fossil fuels, the concentration of CO2 in the earth's atmosphere, which is a potent greenhouse gas, has been increasing dramatically and contributes to the current climate change. Meanwhile, CO2 can be considered as an abundant and inexpensive carbon feedstock, especially if carbon sequestration is required for future fossil fuel-based power stations. Electrochemical reduction of CO2 to form useful chemicals or fuels is a potentially efficient method of CO2 utilization and recycling. The advantage of the electrochemical CO2 reduction is that natural renewable sources, like solar power, wind power, hydropower or nuclear power can supply electric power for CO2 conversion. Various products, such as carbon monoxide, oxalic acid, formic acid, alcohols and hydrocarbons have been reduced from CO2 First in chapter 1, the general remarks about electrochemical reduction of CO2, especially on metal electrodes are introduced. It also includes the introduction of photoelectochemical CO2 reduction and literature review study about electrocatalytic CO2 reduction with organic molecules as mediators and catalysts. In chapter 2, our interest in Mo-based electrocatalysts led us to study the activity of MoO2 for CO2 reduction. MoO2 microparticles indeed act as an active catalyst for the electrochemical reduction of CO2 in organic solvents such as acetonitrile (MeCN) and dimethylformamide (DMF). In the context of this study, it was found that the CO2 reduction activity is much higher at -20 oC than at RT, and it can be promoted by a small amount of water. The selectivity of CO2 reduction depends on the temperature, overpotential and water concentration. Chapter 3 describes the electrochemical reduction of CO2, improved and modified by using imidazolium ionic liquids (ILs) as an electrolyte in organic solvent with MoO2/Pb electrode. The important role of ILs in changing the pathway of the reduction was observed. Particularly, the use of imidazolium ILs instead of tetraalkylammonium salt as an electrolyte altered the product from oxalate to CO. Besides, the overpotential of the CO2 reduction was shifted to the less negative potentials compared to previous work, and the current density as well increased. At a low water concentration, the catalytic activity was promoted and the total Faradaic efficiency (FE) was up to 100% with more than 60% of CO formation. Furthermore, imidazolium ILs together with our MoO2/Pb electrode lowered the overpotential of CO2 reduction by about 40 mV. In addition to the high selectivity for CO formation, the imidazolium ILs can perform a role as co-catalyst for lowering the CO2 reduction potential. Finally, chapter 4 shows the possibility of photoelectrochemical CO2 reduction to extend our research with various catalysts. In this work, we could derive a photoelectrochemical method to deposit Sn/SnOx catalyst on the surface protected cuprous oxide (Cu2O) photocathodes. The deposition of Sn/SnOx catalyst was optimized on the photocathode and it exhibited reliable CO2 reduction activity in a mild aqueous condition. Sn/SnOx-Cu2O photocathode showed the onset potential of the photocurrent at +0.1 V vs. RHE, which is very promising result. At a constant potential electrolysis of -0.1 V vs. RHE, a FE of 50% for formate formation was obtained and the total FE was around 86%

Ionic liquids enhance the electrochemical CO2 reduction catalyzed by MoO2

Several imidazolium-based ionic liquids significantly enhance the activity of MoO2 for electrochemical reduction of CO2. The over-potential of CO2 reduction is as low as 40 mV. The ionic liquids act as both electrolytes and co-catalysts, which not only leads to lower overpotentials, but also alters the product selectivity

Low-Area Four-Channel Controlled Dielectric Breakdown System Design for Point-of-Care Applications

In this study, we propose a low-area multi-channel controlled dielectric breakdown (CDB) system that simultaneously produces several nanopore sensors. Conventionally, solid-state nanopores are prepared by etching or drilling openings in a silicon nitride (SiNx) substrate, which is expensive and requires a long processing time. To address these challenges, a CDB technique was introduced and used to fabricate nanopore channels in SiNx membranes. However, the nanopore sensors produced by the CDB result in a severe pore-to-pore diameter variation as a result of different fabrication conditions and processing times. Accordingly, it is indispensable to simultaneously fabricate nanopore sensors in the same environment to reduce the deleterious effects of pore-to-pore variation. In this study, we propose a four-channel CDB system that comprises an amplifier that boosts the command voltage, a 1-to-4 multiplexer, a level shifter, a low-noise transimpedance amplifier and a data acquisition device. To prove our design concept, we used the CDB system to fabricate four nanopore sensors with diameters of <10 nm, and its in vitro performance was verified using λ-DNA samples

Structural and functional characterization of USP47 reveals a hot spot for inhibitor design

Abstract USP47 is widely involved in tumor development, metastasis, and other processes while performing a more regulatory role in inflammatory responses, myocardial infarction, and neuronal development. In this study, we investigate the functional and biochemical properties of USP47, whereby depleting USP47 inhibited cancer cell growth in a p53-dependent manner—a phenomenon that enhances during the simultaneous knockdown of USP7. Full-length USP47 shows higher deubiquitinase activity than the catalytic domain. The crystal structures of the catalytic domain, in its free and ubiquitin-bound states, reveal that the misaligned catalytic triads, ultimately, become aligned upon ubiquitin-binding, similar to USP7, thereby becoming ready for catalysis. Yet, the composition and lengths of BL1, BL2, and BL3 of USP47 differ from those for USP7, and they contribute to the observed selectivity. Our study provides molecular details of USP47 regulation, substrate recognition, and the hotspots for drug discovery by targeting USP47

Dual-light emitting 3D encryption with printable fluorescent-phosphorescent metal-organic frameworks

Abstract Optical encryption technologies based on room-temperature light-emitting materials are of considerable interest. Herein, we present three-dimensional (3D) printable dual-light-emitting materials for high-performance optical pattern encryption. These are based on fluorescent perovskite nanocrystals (NCs) embedded in metal-organic frameworks (MOFs) designed for phosphorescent host-guest interactions. Notably, perovskite-containing MOFs emit a highly efficient blue phosphorescence, and perovskite NCs embedded in the MOFs emit characteristic green or red fluorescence under ultraviolet (UV) irradiation. Such dual-light-emitting MOFs with independent fluorescence and phosphorescence emissions are employed in pochoir pattern encryption, wherein actual information with transient phosphorescence is efficiently concealed behind fake information with fluorescence under UV exposure. Moreover, a 3D cubic skeleton is developed with the dual-light-emitting MOF powder dispersed in 3D-printable polymer filaments for 3D dual-pattern encryption. This article outlines a universal principle for developing MOF-based room-temperature multi-light-emitting materials and a strategy for multidimensional information encryption with enhanced capacity and security