Influence of NH4Cl additive in a VO2+/VO2+ - AQDS/AQDS2− solar redox flow battery

Solar redox flow batteries are a relatively new type of redox flow battery technology that uses solar energy to directly store chemical energy. Here we present a solar redox flow battery that uses a MoS2@TiO2 thin film with a Nafion protection layer supported on FTO glass substrate as photoanode, employing VO2+/VO2+ and AQDS/AQDS2− as redox active species. When the solar radiation strikes the photoelectrode, the photogenerated holes oxidize VO2+ to VO2+, while the photogenerated electrons reduce AQDS to AQDS2− at the counter electrode. The oxidized form of V5+ and reduced form of AQDS2− thus retain the chemical energy and can release the stored charged via the reverse electrochemical reaction. The addition of NH4Cl to the electrolyte was found to have a positive impact on the electrochemical performance of the redox flow cell. This effect was more evident for the VOSO4 electrolyte, leading to an enhancement of the voltaic and energy efficiencies of more than 17.5%. The results suggest that NH4Cl promotes both mass transport of the vanadium redox species and charge transfer of the AQDS in the electrolyte. The solar-to-output energy conversion efficiency (SOEE) of the solar redox flow battery using 1.6 g L−1 NH4Cl in both anolyte and catholyte reached 9.73%, and an energy density of 87.45% after 10 consecutive one-hour photocharging cycles. Additionally, the use of Nafion to protect the MoS2@TiO2 photoanode from photocorrosion was explored. The Nafion layer ensured an increased stability of MoS2@TiO2 against the strong acidic environment while maintaining effective light response, which translated into enhanced photon and mass transport. An energy storage capacity of ∼60 mAh L−1 after 1-hour photocharging was observed

Exploring the length scales, timescales and chemistry of challenging materials (Part 1).

This themed issue explores the different length scales and timescales that determine the physics and chemistry of a variety of key materials, explored from the perspective of a wide range of disciplines, including physics, chemistry, materials science, Earth science and biochemistry. The topics discussed include catalysis, chemistry under extreme conditions, energy materials, amorphous and liquid structure, hybrid organic materials and biological materials. The issue is in two parts, with the present part exploring glassy and amorphous systems and materials at high pressure. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'

High-power nitrided TiO2 carbon felt as the negative electrode for all-vanadium redox flow batteries

This work describes the design of an electrode with enhanced performance applied to all-vanadium redox flow batteries (VRFBs). This new electrode consists of a structural porous carbon felt decorated with TiO2 rutile nanoparticles, which has been nitrided using ammonolysis at 900 °C. An outstanding charge and mass transfer over the electrode-electrolyte interface was observed as a consequence of the synergetic effect of N- and O-functionalization over carbon felt (CF) and the partial formation of TiN (metallic conductor) phase. Moreover, this material has not only improved in terms of catalysis towards the V3+/V2+ redox reaction (k0 = 1.6 × 10−3 cm s−1), but also inhibited the hydrogen evolution reaction (HER), which is one of the main causes of imbalances that lead to battery failure. This led to an impressive high-power peak output value up to 700 mW cm−2, as well as work at high current density in galvanostatic conditions (i.e. 150 mA cm−2), exhibiting low ohmic losses (overpotential) and great redox single cell reversibility, with a superior energy efficiency of 71%. An inexpensive, earth abundant and scalable synthesis method to boost VRFBs technology based on nitrided CF@TiO2 is presented, being able to overcome certain constrains, and therefore to achieve high energy and power densities

Photoelectrochemical water splitting with ITO/WO3/BiVO4/CoPi multishell nanotubes fabricated by soft-templating in vacuum

A well-established procedure for the photoelectrochemical (PEC) splitting of water relies on using porous electrodes of WO3 sensitized with BiVO4 as a visible scavenger photoanode semiconductor. In this work, we propose an evolved photoelectrode fabricated by a soft-template approach consisting of supported multishell nanotubes (NTs). These NTs are formed by a concentric layered structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final film of cobalt phosphate (CoPi) co-catalyst. Photoelectrode manufacturing is easily implemented at large scale and combines thermal evaporation of single crystalline organic nanowires (ONWs), magnetron sputtering (for ITO and WO3), solution dripping, and electrochemical deposition processes (for BiVO4 and CoPi, respectively) plus annealing under mild conditions. The obtained NT electrodes depict a large electrochemically active surface and outperform by more than one order of magnitude the efficiency of equivalent planar-layered electrodes. A thorough electrochemical analysis of the electrodes under blue and solar light illumination demonstrates the critical role of the WO3/BiVO4 Schottky barrier heterojunction in the control of the NT electrode efficiency and its dependence on the BiVO4 outer layer thickness. Oxygen evolution reaction (OER) performance was maximized with the CoPi electrocatalyst, rendering high photocurrents under one sun illumination. The reported results demonstrate the potential of the soft-template methodology for the large area fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes, or other alternative combinations, for the photoelectrochemical splitting of water.Comment: Manuscript: 39 pages, 8 figures and 1 table. SI: 15 pages, 9 figures and 1 tabl

Exploring the length scales, timescales and chemistry of challenging materials (Part 2)

This themed issue explores the different length and timescales that determine the physics and chemistry of a variety of key of materials, explored from the perspective of a wide range of disciplines, including physics, chemistry materials science, Earth science and biochemistry. The topics discussed include catalysis, chemistry under extreme conditions, energy materials, amorphous and liquid structure, hybrid organic materials and biological materials. The issue is in two parts, with this second set of contributions exploring hybrid organic materials, catalysis low-dimensional and graphitic materials, biological materials and naturally occurring, super-hard material as well as dynamic high pressure and new developments in imaging techniques pressure. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 2)'

Recent Advances in Ultralow-Pt-Loading Electrocatalysts for the Efficient Hydrogen Evolution

Hydrogen production from water electrolysis provides a green and sustainable route. Platinum (Pt)-based materials have been regarded as efficient electrocatalysts for the hydrogen evolution reaction (HER). However, the large-scale commercialization of Pt-based catalysts suffers from the high cost. Therefore, ultralow-Pt-loading electrocatalysts, which can reach the balance of low cost and high HER performance, have attracted much attention. In this review, representative promising synthetic strategies, including wet chemistry, annealing, electrochemistry, photochemistry, and atomic layer deposition are summarized. Further, the interaction between different electrocatalyst components (transition metals and their derivatives) and Pt is discussed. Notably, this interaction can effectively accelerate the kinetics of the HER, enhancing the catalytic activity. At last, current challenges and future perspectives are briefly discussed

Exploring the length scales, timescales and chemistry of challenging materials (Part 1)

This themed issue explores the different length scales and timescales that determine the physics and chemistry of a variety of key materials, explored from the perspective of a wide range of disciplines, including physics, chemistry, materials science, Earth science and biochemistry. The topics discussed include catalysis, chemistry under extreme conditions, energy materials, amorphous and liquid structure, hybrid organic materials and biological materials. The issue is in two parts, with the present part exploring glassy and amorphous systems and materials at high pressure. This article is part of the theme issue 'Exploring the length scales, timescales and chemistry of challenging materials (Part 1)'

Synthesis of graphene-encapsulated Fe3C/Fe catalyst supported on Sporopollenin exine capsules, and its use for the reverse water gas shift reaction

Bioderived materials have emerged as sustainable catalyst supports for several heterogeneous reactions owing to their naturally occurring hierarchal pore size distribution, high surface area, and thermal and chemical stability. We utilize sporopollenin exine capsules (SpECs), a carbon-rich byproduct of pollen grains, composed primarily of polymerized and cross-linked lipids, to synthesize carbon-encapsulated iron nanoparticles via evaporative precipitation and pyrolytic treatments. The composition and morphology of the macroparticles were influenced by the precursor iron acetate concentration. Most significantly, the formation of crystalline phases (Fe3C, α-Fe, and graphite) detected via X-ray diffraction spectroscopy showed a critical dependence on iron loading. Significantly, the characteristic morphology and structure of the SpECs were largely preserved after high-temperature pyrolysis. Analysis of Brunauer–Emmett–Teller surface area, the D and G bands from Raman spectroscopy, and the relative ratio of the C═C to C–C bonding from high-resolution X-ray photoelectron spectroscopy suggests that porosity, surface area, and degree of graphitization were easily tuned by varying the Fe loading. A mechanism for the formation of crystalline phases and meso-porosity during the pyrolysis process is also proposed. SpEC-Fe10% proved to be highly active and selective for the reverse water–gas shift reaction at high temperatures (>600 °C)

Analysis of Arterial Blood Gas Values Based on Storage Time Since Sampling: An Observational Study

[Abstract] Aim: To evaluate the influence of time on arterial blood gas values after artery puncture is performed. Method: Prospective longitudinal observational study carried out with gasometric samples from 86 patients, taken at different time intervals (0 (T0), 15 (T15), 30 (T30) and 60 (T60) min), from 21 October 2019 to 21 October 2020. The study variables were: partial pressure of carbon dioxide, bicarbonate, hematocrit, hemoglobin, potassium, lactic acid, pH, partial pressure of oxygen, saturation of oxygen, sodium and glucose. Results: The initial sample consisted of a total of 90 patients. Out of all the participants, four were discarded as they did not understand the purpose of the study; therefore, the total number of participants was 86, 51% of whom were men aged 72.59 on average (SD: 16.23). In the intra-group analysis, differences in PCO2, HCO3, hematocrit, Hb, K+ and and lactic acid were observed between the initial time of the test and the 15, 30 and 60 min intervals. In addition, changes in pH, pO2, SO2, Na and glucose were noted 30 min after the initial sample had been taken. Conclusions: The variation in the values, despite being significant, has no clinical relevance. Consequently, the recommendation continues to be the analysis of the GSA at the earliest point to ensure the highest reliability of the data and to provide the patient with the most appropriate treatment based on those results