FTIR-Assisted Electroreduction of CO2 and H2O to CO and H2 by Electrochemically Deposited Copper on Oxidized Graphite Felt.

Obtaining CO and H2 from electrochemical CO2 reduction (CO2RR) offers a viable alternative to reduce CO2 emissions and produce chemicals and fuels. Herein, we report a simple strategy for obtaining polycrystalline copper deposited on oxidized graphite felt (Cu-OGF) and its performance on the selective conversion of CO2 and H2O to CO and H2. For the electrode obtaining, graphite felt (GF) was first oxidized (OGF) in order to make the substrate hydrophilic and then copper particles were electrochemically deposited onto OGF. The pH of deposition was investigated, and the CO2RR activity was assessed for the prepared electrodes at each pH (2.0, 4.0, 6.0, 8.0, and 10.0). It was found that pH 2.0 was the most promising for CO2RR due to the presence of hexagonal copper microparticles. Fourier transform infrared analysis of the produced gases showed that this is a low-cost catalyst capable of reducing CO2 and H2O to CO and H2, with Faradaic efficiencies between 0.50 and 5.21% for CO and 50.87 to 98.30% for H2, depending on the experimental conditions. Hence, it is possible for this gas mixture to be used as a fuel gas or to be enriched with CO for use in Fischer-Tropsch processes.

Understanding the fundamental electrical and photoelectrochemical behavior of a hematite photoanode.

Hematite is considered to be the most promising material used as a photoanode for water splitting and here we utilized a sintered hematite photoanode to address the fundamental electrical, electrochemical and photoelectrochemical behavior of this semiconductor oxide. The results presented here allowed us to conclude that the addition of Sn(4+) decreases the grain boundary resistance of the hematite polycrystalline electrode. Heat treatment in a nitrogen (N2) atmosphere also contributes to a decrease of the grain boundary resistance, supporting the evidence that the presence of oxygen is fundamental for the formation of a voltage barrier at the hematite grain boundary. The N2 atmosphere affected both doped and undoped sintered electrodes. We also observed that the heat treatment atmosphere modifies the surface states of the solid-liquid interface, changing the charge-transfer resistance. A two-step treatment, with the second being performed at a low temperature in an oxygen (O2) atmosphere, resulted in a better solid-liquid interface.

Single-Step Exfoliation and Covalent Functionalization of MoS2 Nanosheets by an Organosulfur Reaction.

A simple approach to exfoliate and functionalize MoS2 in a single-step is described, which combines the dispersion of MoS2 in polybutadiene solution and ultrasonication processes. The great advantage of this process is that a colloidal stability of MoS2 in nonpolar solvent is achieved by chemically bonding polybutadiene on the perimeter edge sites of MoS2 sheets. In addition, elastomeric nanocomposite has been prepared with singular mechanical properties using functionalized MoS2 as nanofiller in a polybutadiene matrix with a subsequent vulcanization reaction.

Colloidal WO(3) nanowires as a versatile route to prepare a photoanode for solar water splitting.

This work describes a synthetic method to produce a WO(3) nanowire as well as to prepare photoanodes by colloidal nanowire deposition. We also studied the influence of a nanowire phase on the photoanode performance for water splitting. Among the nanowires synthesized by using nonhydrolytic media, the orthorhombic WO(3)·H(2) O nanowire produced a photoanode with excellent performance (a photocurrent of 1.96 mA cm(-2) at 1.23 V(RHE) ) and good photocurrent stability during long-term analysis (chronoamperometry test). The structural and photoelectrochemical characterization showed the importance of nanostructural features such as exposed (200), (020), and (002) facets and porosity in the WO(3) photoanode performance.

Magnetite colloidal nanocrystals: a facile pathway to prepare mesoporous hematite thin films for photoelectrochemical water splitting.

In this study, we demonstrate an alternative and promising way to produce hematite photoanodes with high performance and without the addition of doping or catalytic coating. In this approach, we processed hematite thin films using a colloidal dispersion of magnetite nanocrystals as the precursor. The photoelectrochemical characterization shows that the colloidal approach used to process an undoped hematite photoanode produced a high-performance electrode for water photooxidation with an onset potential as low as 0.8 V(RHE). This value is comparable to the best results reported in the literature for a hematite photoanode modified with catalytic materials. We demonstrate that pure hematite thin films reach 1.1 mA·cm(-2) at 1.23 V(RHE) with back-side illumination.

Synthesis of recrystallized anatase TiO2 mesocrystals with Wulff shape assisted by oriented attachment.

In this work, we describe a kinetically controlled crystallization process assisted by an oriented attachment (OA) mechanism based on a nonaqueous sol-gel synthetic method (specifically, the reaction of titanium(IV) chloride (TiCl(4)) with n-octanol) to prepare re-crystallized anatase TiO(2) mesocrystals (single crystal). The kinetics study revealed a multi-step and hierarchical process controlled by OA, and a high resolution transmission electron microscopy (HRTEM) analysis clearly shows that the synthesized mesocrystal presents a truncated bipyramidal Wulff shape, indicating that its surface is dominated by {101} facets. This shape is developed during the recrystallization step. The material developed here displayed superior photocatalytic activity under visible light irradiation compared to TiO(2)-P25 as a benchmarking.

Synthesis of TiO2 nanocrystals with a high affinity for amine organic compounds.

This article describes a different approach to the colloidal synthesis of TiO(2) nanocrystals using a polymer melt as a solvent. This approach allowed us to obtain a colloidal dispersion with a high degree of stability in a polymeric solvent, resulting in a transparent colloid. Using this method, it was possible to obtain the TiO(2) nanocrystal with Brønsted acid sites and polymer chains chemically anchored on the nanocrystal surface. The acid surface of those nanocrystals has the chemical property to react in the presence of amine organic compounds and to maintain the colloidal stability. In this way, TiO(2) nanocrystals were combined with a molecular probe containing amine functional groups such as polyaniline. Through the combination of the molecular probe and inorganic nanocrystals, we obtained a hybrid material with interesting chemical, optical, and electronic behavior, making it a promising material for photovoltaic, photochromic, and sensor devices.