Sustained, Photocatalytic CO₂ Reduction to CH₄ in a Continuous Flow Reactor by Earth-Abundant Materials: Reduced Titania-Cu₂O Z-Scheme Heterostructures

Photocatalytic conversion of CO₂ and water vapor to hydrocarbon fuels is a promising approach for storing solar energy while reducing greenhouse gas emissions. However, still certain issues including low product yields, limited photocatalyst stability and relatively high cost have hampered practical implementation of this technology. In the present work, a unique strategy is adopted to synthesize a stable, and inexpensive photocatalyst comprised of earth-abundant materials: a reduced titania-Cu₂O Z-scheme heterostructure. Under illumination for 6 h, the optimized reduced titania-Cu₂O photocatalyst enables 0.13 % photoreduction of highly diluted CO₂ with water vapors to 462nmol g⁻¹ of CH₄ while showing excellent stability over seven testing cycles (42 h). Our studies show the Z-scheme inhibits Cu₂O photocorrosion, while its synergistic effects with reduced titania result in sustained CH₄ formation in a continuous flow photoreactor. To the best of our knowledge stability exhibited by the reduced titania-Cu₂O Z-scheme is the highest for any Cu-based photocatalyst

CO_2, water, and sunlight to hydrocarbon fuels: a sustained sunlight to fuel (Joule-to-Joule) photoconversion efficiency of 1%

If we wish to sustain our terrestrial ecosphere as we know it, then reducing the concentration of atmospheric CO_2 is of critical importance. An ideal pathway for achieving this would be the use of sunlight to recycle CO_2, in combination with water, into hydrocarbon fuels compatible with our current energy infrastructure. However, while the concept is intriguing such a technology has not been viable due to the vanishingly small CO_2-to-fuel photoconversion efficiencies achieved. Herein we report a photocatalyst, reduced blue-titania sensitized with bimetallic Cu–Pt nanoparticles that generates a substantial amount of both methane and ethane by CO_2 photoreduction under artificial sunlight (AM1.5): over a 6 h period 3.0 mmol g^(−1) methane and 0.15 mmol g^(−1) ethane are obtained (on an area normalized basis 0.244 mol m^(−2) methane and 0.012 mol m^(−2) ethane), while no H_2 nor CO is detected. This activity (6 h) translates into a sustained Joule (sunlight) to Joule (fuel) photoconversion efficiency of 1%, with an apparent quantum efficiency of φ = 86%. The time-dependent photoconversion efficiency over 0.5 h intervals yields a maximum value of 3.3% (φ = 92%). Isotopic tracer experiments confirm the hydrocarbon products originate from CO_2 and water

에너지 변환을 위한 합성, 분석 및 응용: 광촉매에 의한 이산화탄소 환원과 베타전지

Energy Conversion, Radiation energy, Energy Absorber, CO2 reduction, Betavoltaic cellNDoctordCollectio

Reduced TiO2 quantum dots/graphene for solar light driven CO2 reduction into precisely controlled C-1 vs C-2 hydrocarbon products without noble Co-catalyst

Photocatalytic CO2 reduction is a logical approach to overcome the energy crisis as well as to curb the anthropogenic CO2 emission by converting atmospheric CO2 with water vapour under irradiation into hydrocarbon fuels. Herein, for the first time, a noble metal-free photocatalyst comprised of reduced TiO2 quantum dots (TQDs) dispersed over graphene sheets has been successfully synthesized and employed for this reaction. EELS investigation reveals the addition of graphene has imparted oxygen vacancies inside TQDs, which in turn helps to enhance broad solar light absorption. TRPL spectroscopy revealed a prolonged charge separation in the heterostructure. Depending on graphene content, the ratio of the products has been changed; CH4:C2H6 from 3.41:1 to 1:1.62. The optimized sample exhibits 2.8- and 3.7-fold increment of CH4 and C2H6 yields compared to TQDs. Under the continuous mode, the photocatalyst has shown excellent stability of 72 h. © 2022 Elsevier B.V.FALS

Sustained, photocatalytic CO2 reduction to CH4 in a continuous flow reactor by earth-abundant materials: Reduced titania-Cu2O Z-scheme heterostructures

Photocatalytic conversion of CO2 and water vapor to hydrocarbon fuels is a promising approach for storing solar energy while reducing greenhouse gas emissions. However, still certain issues including low product yields, limited photocatalyst stability and relatively high cost have hampered practical implementation of this technology. In the present work, a unique strategy is adopted to synthesize a stable, and inexpensive photocatalyst comprised of earth-abundant materials: a reduced titania-Cu2O Z-scheme heterostructure. Under illumination for 6 h, the optimized reduced titania-Cu2O photocatalyst enables 0.13 % photoreduction of highly diluted CO2 with water vapors to 462nmol g−1 of CH4 while showing excellent stability over seven testing cycles (42 h). Our studies show the Z-scheme inhibits Cu2O photocorrosion, while its synergistic effects with reduced titania result in sustained CH4 formation in a continuous flow photoreactor. To the best of our knowledge stability exhibited by the reduced titania-Cu2O Z-scheme is the highest for any Cu-based photocatalyst. © 2020 Elsevier B.V.1

Synthesis and Growth Mechanism of Stable Prenucleated (≈0.8 nm Diameter) PbS Quantum Dots by Medium Energy Ion Scattering Spectroscopy

In the current work, stable prenucleated PbS quantum dots (QDs) with a sub-nanometer (0.8 nm) size have been successfully synthesized via a systematically designed experiment. A detailed analysis of critical nucleation, growth, and stability for such ultrasmall prenucleated clusters is done. The experimental strategy is based on controlled concentration, temperature and injection of respective precursors, thus enabling us to control nucleation rate and separation of stable sub-nanometer PbS QDs with size 0.8 nm. Significantly, by providing additional thermal energy to sub-nanometer PbS QDs, we achieved the fully nucleated cubic crystalline structure of PbS with size of around 1.5 nm. The size and composition of the prenucleated QDs are investigated by sophisticated tools like X-ray photoelectron spectroscopy (XPS) and medium energy ion scattering (MEIS) spectroscopy which confirms the synthesis of PbS with Pb2+ rich surface while the UV-Vis spectroscopy and X-ray diffraction (XRD) data suggests an alternative crystallization path. Non-classical nucleation theory is employed to substantiate the growth mechanism of prenucleated PbS QDs

Sustained, Photocatalytic CO₂ Reduction to CH₄ in a Continuous Flow Reactor by Earth-Abundant Materials: Reduced Titania-Cu₂O Z-Scheme Heterostructures

Photocatalytic conversion of CO₂ and water vapor to hydrocarbon fuels is a promising approach for storing solar energy while reducing greenhouse gas emissions. However, still certain issues including low product yields, limited photocatalyst stability and relatively high cost have hampered practical implementation of this technology. In the present work, a unique strategy is adopted to synthesize a stable, and inexpensive photocatalyst comprised of earth-abundant materials: a reduced titania-Cu₂O Z-scheme heterostructure. Under illumination for 6 h, the optimized reduced titania-Cu₂O photocatalyst enables 0.13 % photoreduction of highly diluted CO₂ with water vapors to 462nmol g⁻¹ of CH₄ while showing excellent stability over seven testing cycles (42 h). Our studies show the Z-scheme inhibits Cu₂O photocorrosion, while its synergistic effects with reduced titania result in sustained CH₄ formation in a continuous flow photoreactor. To the best of our knowledge stability exhibited by the reduced titania-Cu₂O Z-scheme is the highest for any Cu-based photocatalyst

Study of β-lactam induced bacteriolysis using high-throughput time-resolved microscopy and mechanical bacteriolysis by nanostructured surfaces

Bacteriolysis is one of the most widely used modes of killing bacteria. β-lactam antibiotics, antimicrobial peptides, glycopeptides, phage therapy and nanostructured antibacterial surfaces kill bacteria principally by inducing lysis. A deeper understanding of the process of bacteriolysis can inspire new ways to prevent bacterial colonization and increase antibiotic efficacy. In the first part of this work, we develop a high-throughput microscopy-based methodology to monitor morphological changes in bacteria due to environmental perturbation. Using off-the-shelf microscopy hardware and software utilities we implement a protocol for imaging bacteria in 96-well plates. To demonstrate the capabilities of the method, we monitored morphological changes and lysis of around 4000 Escherichia coli mutants in response to the β-lactam antibiotic cefsulodin. We also established a novel image analysis pipeline for automated classification of cells based on their shape and intensity features. Based on changes in frequencies of cell morphotypes we identified mutants that displayed atypical morphological dynamics. The aberrant phenotypes were further clustered to reveal the distinct morphological responses of mutants to cefsulodin. Stable bulge formation in certain mutants promotes antibiotic tolerance, as bulging cells are capable of reverting back to normal growth after the antibiotic is removed. This methodology is highly versatile and can be applied to find genetic modulators of bacterial morphological responses to different kinds of perturbations like antibiotics. In the second part of this thesis, we applied the imaging methodology developed in the first part to measure lysis kinetics of around 4000 E. coli mutants in response to the β-lactam antibiotic cephalexin. We found that the period of filamentation before lysis differs widely among the mutants and that lysis kinetics correlate with survival. Delay in lysis confers antibiotic tolerance because when the antibiotic is removed, the filamented cells can successfully form multiple septations simultaneously and divide into multiple progenies. We found that deletion of tol-pal genes tolQ, tolR, ybgC and pal results in rapid lysis without filamentation upon treatment with β-lactams. These results emphasize the importance of considering antibiotic tolerance during antibiotic therapy. In the final part, we describe the antibacterial activity of cotton swab shaped nanostructures. These nanostructures kill bacteria in a physical contact-dependent manner. A biophysical model was developed from infinitesimal strain theory to investigate the effects of changes in surface topography on the bactericidal activity. We made several controlled geometrical alterations of the cotton swab shaped nanostructures. Measurement of bactericidal activities of these nanostructured surfaces confirmed model predictions and highlighted the non-trivial role of cell envelope bending rigidity in the process of bacteriolysis by nanostructures. In conclusion, the high-throughput time-resolved morphology screening methodology presented in this work provides an easy-to-implement protocol for rapid imaging of large number of bacterial strains and analyzing single-cell morphological changes in response to any perturbant. Additionally, results presented in this thesis yield novel insights that will potentially contribute to the development of better prevention and treatment strategies needed to successfully combat bacterial infections.status: publishe