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Electrochemical reduction of carbon dioxide (CO2RR) to crystalline solid carbon at room temperature is challenging, but it is a providential CO2 utilization route due to its indefinite storage and potential applications of its products in many advanced technologies. Here, room-temperature synthesis of polycrystalline nanographene was achieved by CO2RR over the electrodeposited Bi on Sn substrate prepared with various bismuth concentrations (0.01 M, 0.05 M, and 0.1 M). The solid carbon products were solely produced on all the prepared electrodes at the applied potential −1.1 V vs. Ag/AgCl and were characterized as polycrystalline nanographene with an average domain size of ca. 3–4 nm. The morphology of the electrodeposited Bi/Sn electrocatalysts did not have much effect on the final structure of the solid carbon products formed but rather affected the CO2 electroreduction activity. The optimized negative potential for the formation of nanographene products on the 0.05Bi/Sn was ca. −1.5 V vs. Ag/AgCl. Increasing the negative value of the applied potential accelerated the agglomeration of the highly reactive nascent Bi clusters in situ formed under the reaction conditions, which, as a consequence, resulted in a slight deviation of the product selectivity toward gaseous CO and H2 evolution reaction. The Bi–graphene composites produced by this method show high potential as an additive for working electrode modification in electrochemical sensor-related applications.

In the present study, a systematic investigation is performed to assess the relationship between electroplating parameters, pore morphology and internal surface area of copper deposits which are promising to serve as electrodes for electrochemical reduction reactions of carbon dioxide (CO2). A set of porous copper deposits are fabricated with the dynamic hydrogen bubble template method. The microstructural and Brunauer–Emmett–Teller (BET) analysis demonstrate that current density, deposition time, and bath composition control pore size, strut size, and hence surface area which could be as high as 20 m2/g. Selected sets of porous copper electrodes are then employed in the electrochemical reduction reaction test to determine their conversion performance in comparison to a monolithic copper surface. From the gas chromatography (GC) and nuclear magnetic resonance (NMR) analysis, porous copper is shown to provide higher rates of production of some important chemicals, as compared to copper foil electrodes. Porous copper with fern-like morphology serves as a promising electrode that yields relatively high amounts of acetaldehyde, acetate and ethanol. The study thus presents the opportunities to enhance the electrochemical reduction reaction of CO2 through microstructural engineering of the copper surface, which benefits both CO2 reduction and generation of chemical products of high value.

The modification of zeolite A (NaA) by impregnation with different concentrations of silver ions (Ag+) or silver nanoparticles (AgNPs) for antibacterial activity was investigated. The Ag+-NaA composites were prepared by ion exchange against different concentrations of silver nitrate solution (25-200 mg/L) while AgNPs were subsequently prepared by reducing the impregnated Ag+ with sodium borohydride. The addition of Ag+ and AgNPs had no discernible effect on the NaA structure. The AgNPs in the AgNP-NaA composites exhibited a typical broad absorption peak at 394 nm that was absent in the Ag+-NaA composites. The Ag+-NaA and AgNP-NaA composites both showed a dose- and time-dependent antimicrobial activity against the Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli bacteria, but were substantially more effective against E. coli than S. aureus. Moreover, Ag+-NaA composites had a substantially higher antibacterial efficiency against E. coli than the AgNP-NaA composites, whereas the highest concentration at 3 h, the AgNP-NaA composites were weakly more effective than the Ag+-NaA composites against S. aureus. [ABSTRACT FROM AUTHOR]