Solar carbon fuel via photoelectrochemistry

A promising strategy to mitigate both energy shortage and global warming is the conversion of CO2 into chemicals that can be used as fuels (chemical fuels) by utilizing renewable energy sources. Up to date, solar-driven CO2 reduction has been achieved with photochemical (PC) and photoelectrochemical (PEC) systems or electrochemical cells combined with a photovoltaic system (PV-EC). This study is intended to compare and highlight the state-of-the-art PEC systems for CO2 reduction and show the limitation factors that still hinder their widespread utilization. The review starts with a description of semiconducting photocatalyst properties and fundamental understanding of PEC CO2 reduction process. Then, the most significant performance metrics used for evaluation of PEC systems are explained in details. In addition, recent progress in PEC CO2 reduction systems is summarized and classified in different categories according to the chemical product. Different strategies such as doping, combination of two or more semiconductors, synthesis of nanostructured materials, passivation layers and co-catalysts that enhance light absorption, chemical stability, charge transfer and reduce ohmic losses and overpotentials of photoactive materials are reviewed. Besides the improvement of photocatalysts, research progress on the front of PEC reactor design, combined with the development of advanced modelling tools and characterization techniques are expected to bring PEC CO2 reduction a step closer to commercialization

Expression of neurogenin3 reveals an islet cell precursor population in the pancreas

Differentiation of early gut endoderm cells into the endocrine cells forming the pancreatic islets of Langerhans depends on a cascade of gene activation events controlled by transcription factors including the basic helix-loop-helix (bHLH) proteins. To delineate this cascade, we began by establishing the position of neurogenin3, a bHLH factor found in the pancreas during fetal development. We detect neurogenin3 immunoreactivity transiently in scattered ductal cells in the fetal mouse pancreas, peaking at embryonic day 15.5. Although not detected in cells expressing islet hormones or the islet transcription factors Isl1, Brn4, Pax6 or PDX1, neurogenin3 is detected along with early islet differentiation factors Nkx6.1 and Nkx2.2, establishing that it is expressed in immature cells in the islet lineage. Analysis of transcription factor-deficient mice demonstrates that neurogenin3 expression is not dependent on neuroD1/BETA2, Mash1, Nkx2.2, Nkx6.1, or Pax6. Furthermore, early expression of neurogenin3 under control of the Pdx1 promoter is alone sufficient to drive early and ectopic differentiation of islet cells, a capability shared by the pancreatic bHLH factor, neuroD1/BETA2, but not by the muscle bHLH factor, MyoD. However, the islet cells produced in these transgenic experiments are overwhelmingly α cells, suggesting that factors other than the bHLH factors are required to deviate from a default α cell fate. These data support a model in which neurogenin3 acts upstream of other islet differentiation factors, initiating the differentiation of endocrine cells, but switching off prior to final differentiation. The ability to uniquely identify islet cell precursors by neurogenin3 expression allows us to determine the position of other islet transcription factors in the differentiation cascade and to propose a map for the islet cell differentiation pathway

Hybrid redox flow cells with enhanced electrochemical performance via binderless and electrophoretically deposited nitrogen-doped graphene on carbon paper electrodes.

Hybrid redox flow cells (HRFC) are key enablers for the development of reliable large-scale energy storage systems; however, their high cost, limited cycle performance, and incompatibilities associated with the commonly used carbon-based electrodes undermine HRFC's commercial viability. While this is often linked to lack of suitable electrocatalytic materials capable of coping with HRFC electrode processes, the combinatory use of nanocarbon additives and carbon paper electrodes holds new promise. Here, by coupling electrophoretically deposited nitrogen-doped graphene (N-G) with carbon electrodes, their surprisingly beneficial effects on three types of HRFCs, namely, hydrogen/vanadium (RHVFC), hydrogen/manganese (RHMnFC), and polysulfide/air (S-Air), are revealed. RHVFCs offer efficiencies over 70% at a current density of 150 mA cm-2 and an energy density of 45 Wh L-1 at 50 mA cm-2, while RHMnFCs achieve a 30% increase in energy efficiency (at 100 mA cm-2). The S-Air cell records an exchange current density of 4.4 × 10-2 mA cm-2, a 3-fold improvement of kinetics compared to the bare carbon paper electrode. We also present cost of storage at system level compared to the standard all-vanadium redox flow batteries. These figures-of-merit can incentivize the design, optimization, and adoption of high-performance HRFCs for successful grid-scale or renewable energy storage market penetration

Evaluation of a non-aqueous vanadium redox flow battery using a deep eutectic solvent and graphene-modified carbon electrodes via electrophoretic deposition

Common issues aqueous-based vanadium redox flow batteries (VRFBs) face include low cell voltage due to water electrolysis side reactions and highly corrosive and environmentally unfriendly electrolytes (3 to 5 M sulfuric acid). Therefore, this investigation looks into the comparison of a highly conductive ionic liquid with a well-studied deep eutectic solvent (DES) as electrolytes for non-aqueous VRFBs. The latter solvent gives 50% higher efficiency and capacity utilization than the former. These figures of merit increase by 10% when nitrogen-doped graphene (N-G)-modified carbon papers, via a one-step binder-free electrophoretic deposition process, are used as electrodes. X-ray computed tomography confirms the enhancement of electrochemical surface area of the carbon electrodes due to N-G while electrochemical impedance spectra show the effect of its higher conductivity on improving RFB performance. Finally, potential strategies for the scaling-up of DES-based VRFBs using a simple economical model are also briefly discussed. From this study, it is deduced that more investigations on applying DESs as non-aqueous electrolytes to replace the commonly used acetonitrile may be a positive step forward because DESs are not only cheaper but also safer to handle, far less toxic, non-flammable, and less volatile than acetonitrile

Tunnel restoration in unstable rock masses: Numerical analysis and validation of monitoring data from innovative instrumentation

The increase of global temperatures caused shortages of water supply in several Italian cities. One of the challenges of responsible institution is how to maintain and restore the old aqueducts facilities. In particular, the most critical problem is related to the water losses along the aqueduct pipes and tunnels due to the aging of the structures and the damages caused by rock mass instabilities. This paper deals with one of these cases, where an aqueduct tunnel, damaged by the progressive movement of a rockslide, underwent to a complete reconstruction. The restoration design required the installation of CIR-Array, an innovative automated monitoring system, which would enable to monitor the surrounding rock mass, as well as the provisional reinforcement and the final lining, during both construction and operational phases. This case has been the first in situ application of this instrumentation and it represents an interesting test, complementary to the previous laboratory one. Construction works are still in progress, as well as the installation of monitoring instrumentations. In this paper, the preliminary results are presented, described and then compared with the expected behavior of the rock mass predicted by the design numerical model

Experimental and Modeling Investigation of CO3=/OH\u2013 Equilibrium Effects on Molten Carbonate Fuel Cell Performance in Carbon Capture Applications

Molten Carbonate Fuel Cells (MCFCs) are used today commercially for power production. More recently they have also been considered for carbon capture from industrial and power generation CO2 sources. In this newer application context, our recent studies have shown that at low CO2/H2O cathode gas ratios, water supplements CO2 in the electrochemical process to generate power but not capture CO2. We now report the direct Raman observation of the underlying carbonate-hydroxide equilibrium in an alkali carbonate eutectic near MCFC operating conditions. Our improved electrochemical model built on the experimental equilibrium data adjusts the internal resistance terms and has improved the representation of the MCFC performance. This fundamentally improved model now also includes the temperature dependence of cell performance. It has been validated on experimental data collected in single cell tests. The average error in the simulated voltage is less than 4% even when extreme operating conditions of low CO2 concentration and high current density data are included. With the improvements, this electrochemical model is suitable for simulating industrial cells and stacks employed in a wide variety of carbon capture applications

Large-scale population genetic analysis for hemoglobinopathies reveals different mutation spectra in central Greece compared to the rest of the country

We have undertaken a large population screening study to identify the molecular basis of hemoglobinopathies in the central Greece region. A total of 845 unrelated beta-thalassemia patients and alpha-, beta-, and delta beta-thalassemia carriers have been recruited and screened for mutations in the a- and P-globin gene clusters. The alpha(-MED) deletion and the Turkish inversion/deletion are the most frequent genetic rearrangements leading to alpha- and delta beta-thalassemia respectively, contrary to the situation in the rest of the country, while the beta-101 (C > T) promoter mutation is surprisingly frequent in the central part of Greece. Our data indicate that determination of mutation frequencies in different regions is vital for accurate provision of genetic services and counseling and for precise estimation of genetic diversity