Amine???Rich Hydrogels Enhance Solar Water Oxidation via Boosting Proton???Coupled Electron Transfer

Photoelectrochemical (PEC) water oxidation is a highly challenging task that acts as a bottleneck for efficient solar hydrogen production. It is because each cycle of water oxidation is composed of four proton-coupled electron transfer (PCET) processes and conventional photoanodes and cocatalysts have limited roles in enhancing the charge separation and storage rather than in enhancing catalytic activity. In this study, a simple and generally applicable strategy to improve the PEC performance of water oxidation photoanodes through their modification with polyethyleneimine (PEI) hydrogel is reported. The rich amine groups of PEI not only allow the facile and stable modification of photoanodes by crosslinking but also contribute to improving the kinetics of PEC water oxidation by boosting the PCET. Consequently, the PEC performance of various photoanodes, such as BiVO4, Fe2O3, and TiO2, is significantly enhanced in terms of photocurrent densities and onset potentials even in the presence of notable cocatalyst, cobalt phosphate. The present study provides new insights into and strategies for the design of efficient photoelectrodes and PEC devices

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

Modular Flow Reactors for Valorization of Kraft Lignin and Low???Voltage Hydrogen Production

Recent studies have found that green hydrogen production and biomass utilization technologies can be combined to efficiently produce both hydrogen and value-added chemicals using biomass as an electron and proton source. However, the majority of them have been limited to proof-of-concept demonstrations based on batch systems. Here the authors report the design of modular flow systems for the continuous depolymerization and valorization of lignin and low-voltage hydrogen production. A redox-active phosphomolybdic acid is used as a catalyst to depolymerize lignin with the production of aromatic compounds and extraction of electrons for hydrogen production. Individual processes for lignin depolymerization, byproduct separation, and hydrogen production with catalyst reactivation are modularized and integrated to perform the entire process in the serial flow. Consequently, this work enabled a one-flow process from biomass conversion to hydrogen gas generation under a cyclic loop. In addition, the unique advantages of the fluidic system (i.e., effective mass and heat transfer) substantially improved the yield and efficiency, leading to hydrogen production at a higher current density (20.5 mA cm???2) at a lower voltage (1.5 V) without oxygen evolution. This sustainable eco-chemical platform envisages scalable co-production of valuable chemicals and green hydrogen for industrial purposes in an energy-saving and safe manner

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

Regulation of the Escherichia coli HipBA Toxin-Antitoxin System by Proteolysis

Bacterial populations produce antibiotic-tolerant persister cells. A number of recent studies point to the involvement of toxin/antitoxin (TA) modules in persister formation. hipBA is a type II TA module that codes for the HipB antitoxin and the HipA toxin. HipA is an EF-Tu kinase, which causes protein synthesis inhibition and dormancy upon phosphorylation of its substrate. Antitoxins are labile proteins that are degraded by one of the cytosolic ATP-dependent proteases. We followed the rate of HipB degradation in different protease deficient strains and found that HipB was stabilized in a lon- background. These findings were confirmed in an in vitro degradation assay, showing that Lon is the main protease responsible for HipB proteolysis. Moreover, we demonstrated that degradation of HipB is dependent on the presence of an unstructured carboxy-terminal stretch of HipB that encompasses the last 16 amino acid residues. Further, substitution of the conserved carboxy-terminal tryptophan of HipB to alanine or even the complete removal of this 16 residue fragment did not alter the affinity of HipB for hipBA operator DNA or for HipA indicating that the major role of this region of HipB is to control HipB degradation and hence HipA-mediated persistence

산소 환원 반응을 위한 용액상에서의 균일한 백금-니켈-마그네슘 삼성분계 합금 촉매의 합성

N1 INTRODUCTION 1 1.1 PEM fuel cell 2 1.2 Component of the PEM fuel cell 3 1.2.1 Membrane 3 1.2.2 Electrode 3 1.2.3 Gas diffusion layer 4 1.2.4 Bipolar pates 4 1.3 Thermodynamic of the PEM fuel cell 5 1.3.1 Fuel cell efficiency 5 1.4 PEM fuel cell reactions 5 1.4.1 Oxygen reduction reaction 5 1.4.2 Hydrogen oxidation reaction 6 1.5 Platinum Group metal catalyst 7 1.5.1 Pt catalyst 9 1.5.2 Pt alloy catalyst 11 2 PHYSICAL AND ELECTROCHEMICAL CHARATERIZATION 12 2.1.1 Physical charaterization 12 2.1.2 Electrochemical charaterization 12 2.1.3 Fuel cell MEA test 13 3 NEW PtNiMg ALLOY CATALYST VIA SOLUTION PHASE FOR OXYGEN REDUCTION REACTION 14 3.1 Introduction 14 3.2 Experimental section 17 3.2.1 Chemicals 17 3.2.2 Synthesis of PtNiMg 17 3.3 Characterization 18 3.4 Electrochemical test 18 3.5 MEA test 19 3.6 Results and discussions 20 3.7 Conclusion 35 3.8 Reference 36 요약문 44MasterdCollectio

Improving performance of water oxidation photoanodes with nanoparticle-polymer hybrid films: Enhanced light-harvesting and catalytic efficiency

Solar water oxidation has received great attention as an efficient way to convert unlimited solar energy into chemical energy for sustainable development. Theoretically, it can be achieved by using a semiconducting material with a suitable bandgap and band-edge positions. Despite considerable efforts for several decades, most semiconducting materials have low photocatalytic performance due to their inherent limitations such as narrow absorption band with a low absorption coefficient, fast recombination of photogenerated excitons, sluggish water oxidation kinetics, and photocorrosion. To address these problems, it is important to develop a comprehensive strategy to modify them with proper functional materials. In this study, we report the development of an efficient water oxidation photoanode (e.g., Fe O and BiVO ) through the integration of various functional substances on their surface using layer-by-layer (LbL) assembly techniques. Various polyelectrolytes were used as an electrostatic adhesive to integrate the following functional materials: plasmonic Ag nanoparticles (NPs), upconversion (UCN) NPs, and polyoxometalate (POM) water oxidation catalysts (WOCs). After the modification with these components, the performance of water oxidation photoanodes was significantly enhanced due to their respective roles: (1) improved light harvesting by effective electron extraction in the band absorption region by Ag NPs, (2) utilization of infrared light by UCN NPs, (3) suppression of surface recombination with polyelectrolyte passivation layers, and (4) increased catalytic activity by POM WOCs. We believe that our approach can provide insights to design and application of LBL-assembled novel electrochemical and otoelectrochemical devices