The electrochemical reduction of CO 2 (CO 2 RR) to high-value products is an attractive means to simultaneously address the negative effects of increasing CO 2 emissions and the ever-present societal demand for chemicals and fuels. However, the rational development of novel catalyst chemistries for this reaction is needed to tune the activity and selectivity of the CO 2 RR, especially for increasingly complex chemistries, such as oxides, sulfides, and phosphides. In this work, we explore a diverse chemical range of transition-metal perovskite oxides (ABO 3 ) by determining their surface binding energies toward CO ads and H ads using density functional theory (DFT) and by evaluating their CO 2 RR activity and selectivity. We find that tuning perovskite chemistry results in the ability to electrochemically reduce CO 2 to CH 4 . We propose the O 2p-band center as a rational design parameter that faithfully captures the energetics of H ads and CO ads binding that influence the hydrogen evolution reaction (HER) and CO 2 RR activity. A higher O 2pband center results in higher HER activity, while an intermediate O 2p-band center improves favorability for CH 4 evolution. In the process, we identify a group of perovskites (i.e., LaCoO 3 , GdCoO 3 , NdCoO 3 ) as materials that have not, to date, been reported previously for CH 4 evolution activity at relatively low overpotentials (−0.6 to −0.8 V RHE ).

Many studies have used nanoscale zero valent iron (nZVI) nanoparticles to remove redox-sensitive metals (e.g., As, Cr, U, Se, Ni, Cu) from aqueous systems by absorption or reduction processes. However, very few investigations present a detailed study of the product formed after the remediation process. In order to quantify the efficiency of nZVI particles as a possible cadmium remediation agent, we prepared nZVI by sodium borohydride reduction of an iron complex, FeCl 3 $6H 2 O, at room temperature and ambient pressure. Fe 0 and nanocrystalline structures of iron oxides and oxyhydroxides were obtained with this method. We exposed the nZVI to 6 ppm of Cd 2+ and characterized the products with X-ray diffraction, X-ray absorption and X-ray photoelectron spectroscopy. Inductively coupled plasma analysis showed that the nZVI remediation efficiency of cadmium ions was between 80% and 90% in aqueous media. All of the physical characterization results confirmed the presence of Fe 0 , a-Fe 2 O 3 and FeOOH. High resolution transmission electron microscopy images showed nanofiber formation of a mixture of Fe 0 , oxyhydroxides and oxides iron formed after interacting with cadmium ions, possibly forming CdFe 2 O 4 .These results suggest that the FeOOH shell and other iron oxides in nZVI could enhance Cd 2+ removal.This removal is observed to cause a change of the initial structure of nZVI to nanofibers due to possible formation of CdFe 2 O 4 as a waste product.

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An electrosynthesis method to obtain Au nanoparticles dispersed on carbon Vulcan XC-72R support material was done using AuX4 – (X = Cl–, Br–, and OH–) as molecular precursors and different electrolyte media. The Au surface structure was significantly enhanced using KOH as an electrolyte as opposed to KBr and H2SO4. Cyclic voltammetry was used as a surface sensitive technique to illustrate the Au/Vulcan XC-72R catalytic activity for the ethanol oxidation reaction (EOR). The Au electroactive surface areas obtained were 1.88, 5.83, and 13.96 m2 g–1 for Au/C–H2SO4, Au/C–KBr, and Au/C–KOH, respectively. The latter compares to chemically reduced Au/C–spheres that had an electroactive surface area of 15.0 m2 g–1. The electrochemical Au electrodeposition, in alkaline media (Au/C–KOH), exhibited the highest catalytic activity for the EOR with a 50% increase in peak current density when compared with Au nanoparticles prepared by the chemical reduction route. Raman and X-ray photoelectron spectroscopies analyses of the Au/Vulcan XC-72R nanomaterials revealed a restructuring of the carbon functionalities responsible for the metal nanoparticle anchoring. Our results strongly suggest that the enhanced EOR catalytic activity is related to the presence of oxygen functional groups on the carbon surface, particularly ketonic groups on the carbon Vulcan XC-72R substrate.

The Rotating Disk Slurry Electrodeposition (RoDSE) technique is a novel method allowing to deposit electrochemically metal nanoparticles on a given conductive support and produce a powder catalyst for diverse applications, for example, ethanol oxidation reaction (EOR). This technique was used to electrodeposit Pd nanoparticles on carbon Vulcan XC-72R nanoflakes at three different applied potentials (0.0, 0.4, and 0.7 V vs. RHE). The potentials were chosen based on different regions of Pd electrodeposition on a clean glassy carbon electrode. Each Pd/Vulcan catalyst was characterized through different spectroscopic, microscopic, and electrochemical techniques. Powder X-ray diffraction and transmission electron microscopy studies verified the Pd crystallinity and particle size, respectively. The Pd particle size decreased with a more positive applied electrodeposition potential at carbon Vulcan XC-72R nanoflakes. X-ray photoelectron spectroscopy determined that the applied potential affected, both, the final palladium and carbon oxidation states. Finally, cyclic voltammetry was used to characterize the electrocatalytic activity of each Pd / Vulcan catalyst in 0.1M KOH and for the EOR. It was found that, for Pd electrodeposition, an applied potential of 0.4 V vs. RHE provided harmony between a mass transport and kinetically controlled deposition thereby providing the optimal conditions to produce a better catalyst with better EOR.