Exploring the CO2 photocatalytic evolution onto the CuO (1 1 0) surface: A combined theoretical and experimental study.

A combined theoretical and experimental study was performed to elucidate the photocatalytic potential of tenorite, CuO (1 1 0) and to assess the evolution pathway of carbon dioxide (CO2) evolution pathway. The calculations were performed with density functional theory (DFT) at a DFT + U + J0 and spin polarized level. The CuO was experimentally synthesized and characterized with structural and optical methodologies. The band structure and density of states revealed the rise of band gaps at 1.24 and 1.03 eV with direct and indirect band gap nature, respectively. These values are in accordance with the experimental evidence at 1.28 and 0.96 eV; respectively, which were obtained by UV-Vis DRS. Such a behavior could be related to enhanced photocatalytic activity among copper oxide materials. Experimental evidence such as SEM images and work function measurements were also performed to evaluate the oxide. The redox potential suggests a catalytic character of tenorite (1 1 0) for the CO2 transformation through aldehydes (methanal) intermediate formation. Furthermore, a route through methylene glycol CH2(OH)2 was also explored with the theoretical methodology. The reaction path exhibits an immediate reduction of Image 1 into a •OH radical and an [OH]- anion, in the first step. This •OH radical attacks a double bond (C = O) of Image 2 to form bicarbonate ([Image 3]-) and subsequently, carbonic acid (Image 4). The carbonic acid reacts with other •OH radical to finally form orthocarbonic acid (Image 5).

Sb2O3 nanoparticles anchored on N-doped graphene nanoribbons as improved anode for sodium-ion batteries.

Sodium-ion batteries (SIBs) are emerging as a promising alternative to conventional lithium-ion technology, due to the abundance of sodium resources. Still, major drawbacks for the commercial application of SIBs lie in the slow kinetic processes and poor cycling performance of the devices. In this work, a hybrid nanocomposite of Sb2O3 nanoparticles anchored on N-doped graphene nanoribbons (GNR) is implemented as anode material in SIBs. The obtained Sb2O3/N-GNR anode delivers a reversible specific capacity of 642 mA h g-1 after 100 cycles at 0.1 A g-1 and exhibits a good rate capability. Even after 500 cycles at 5 A g-1, the specific capacity is maintained at about 405 mA h g-1. Such good Na storage performance is mainly ascribed to the beneficial effect of N doping for charge transfer and to the improved microstructure that facilitates the Na+ diffusion through the overall electrode.

Understanding the interaction between heteroatom-doped carbon matrix and Sb2S3 for efficient sodium-ion battery anodes.

Increasing the electrochemical performance of electrode materials in sodium ion batteries (NIBs) remains a major challenge. Here, a combined experimental and theoretical investigation on the modification induced by Sb2S3 embedded in a heteroatom-doped 3D carbon matrix (CM) for efficient anodes in NIBs is presented. The structural and chemical characterization demonstrates the successful doping of 3D CM with S and Sb atoms. When evaluated as anode materials for NIBs, the heteroatom-doped nanocomposites delivered a better cycling stability and superior rate capability than those of undoped Sb2S3/CM anodes. First principle calculations were used at the Density Functional Theory level to systematically study the Sb2S3/CM and Sb2S3/heteroatom doped-CM composites, as NIBs anodes. Doping the carbon substrate by heteroatoms improved the adsorption of Sb2S3 on the matrix and allowed for ionic/covalent attraction with the Sb2S3 nanoparticle, respectively. Such results could be used to model the stabilty of the composite architectures observed in the experiment, for superior cycling stability.

Modification of Graphene Oxide Membranes by the Incorporation of Nafion Macromolecules and Conductive Scaffolds.

Stable, reproducible and low-cost graphene oxide (GO)/Nafion (N) membranes were fabricated using electronically conductive carbon paper (CP) matts as a scaffold. The presence of polar groups in the Nafion molecule facilitates the strong interaction with functional groups in the GO, which increases GO dispersion and aids the retention of the composite into the CP scaffold. Distribution of GO/N was carefully characterized by X-ray diffraction work function measurements, Raman and scanning electron microscopy analyses. The performance of these membranes was tested with 1 M NaCl at standard conditions, finding 85% ion removal in the best membranes by a mixed ion rejection/retention mechanism. The Nafion provided mechanical stability and fixed negative charge to the membranes, and its micellar organization, segregation and confinement favored ion rejection in Nafion-rich areas. The good electronic conductivity of these membranes was also demonstrated, allowing for the application of a small potential bias to enhance membrane performance in future studies.

Conducting Polymers in the Fields of Energy, Environmental Remediation, and Chemical-Chiral Sensors.

Conducting polymers (CPs), thanks to their unique properties, structures made on-demand, new composite mixtures, and possibility of deposit on a surface by chemical, physical, or electrochemical methodologies, have shown in the last years a renaissance and have been widely used in important fields of chemistry and materials science. Due to the extent of the literature on CPs, this review, after a concise introduction about the interrelationship between electrochemistry and conducting polymers, is focused exclusively on the following applications: energy (energy storage devices and solar cells), use in environmental remediation (anion and cation trapping, electrocatalytic reduction/oxidation of pollutants on CP based electrodes, and adsorption of pollutants) and finally electroanalysis as chemical sensors in solution, gas phase, and chiral molecules. This review is expected to be comprehensive, authoritative, and useful to the chemical community interested in CPs and their applications.

Recombination reduction on lead halide perovskite solar cells based on low temperature synthesized hierarchical TiO2 nanorods.

Intensive research on the electron transport material (ETM) has been pursued to improve the efficiency of perovskite solar cells (PSCs) and decrease their cost. More importantly, the role of the ETM layer is not yet fully understood, and research on new device architectures is still needed. Here, we report the use of three-dimensional (3D) TiO2 with a hierarchical architecture based on rutile nanorods (NR) as photoanode material for PSCs. The proposed hierarchical nanorod (HNR) films were synthesized by a two-step low temperature (180 °C) hydrothermal method, and consist of TiO2 nanorod trunks with optimal lengths of 540 nm and TiO2 nanobranches with lengths of 45 nm. Different device configurations were fabricated with TiO2 structures (compact layer, NR and HNR) and CH3NH3PbI3, using different synthetic routes, as the active material. PSCs based on HNR-CH3NH3PbI3 achieved the highest power conversion efficiency compared to PSCs with other TiO2 structures. This result can be ascribed mainly to lower charge recombination as determined by impedance spectroscopy. Furthermore, we have observed that the CH3NH3PbI3 perovskite deposited by the two-step route shows higher efficiency, surface coverage and infiltration within the structure of 3D HNR than the one-step CH3NH3PbI(3-x)Cl(x) perovskite.

Bright Visible-Infrared Light Emitting Diodes Based on Hybrid Halide Perovskite with Spiro-OMeTAD as a Hole-Injecting Layer.

Hybrid halide perovskites that are currently intensively studied for photovoltaic applications, also present outstanding properties for light emission. Here, we report on the preparation of bright solid state light emitting diodes (LEDs) based on a solution-processed hybrid lead halide perovskite (Pe). In particular, we have utilized the perovskite generally described with the formula CH3NH3PbI(3-x)Cl(x) and exploited a configuration without electron or hole blocking layer in addition to the injecting layers. Compact TiO2 and Spiro-OMeTAD were used as electron and hole injecting layers, respectively. We have demonstrated a bright combined visible-infrared radiance of 7.1 W·sr(-1)·m(-2) at a current density of 232 mA·cm(-2), and a maximum external quantum efficiency (EQE) of 0.48%. The devices prepared surpass the EQE values achieved in previous reports, considering devices with just an injecting layer without any additional blocking layer. Significantly, the maximum EQE value of our devices is obtained at applied voltages as low as 2 V, with a turn-on voltage as low as the Pe band gap (V(turn-on) = 1.45 ± 0.06 V). This outstanding performance, despite the simplicity of the approach, highlights the enormous potentiality of Pe-LEDs. In addition, we present a stability study of unsealed Pe-LEDs, which demonstrates a dramatic influence of the measurement atmosphere on the performance of the devices. The decrease of the electroluminescence (EL) under continuous operation can be attributed to an increase of the non-radiative recombination pathways, rather than a degradation of the perovskite material itself.