Formation of hierarchically-ordered nanoporous silver foam and its electrocatalytic properties in reductive dehalogenation of organic compounds

New J. Chem. 2018, 42 (21), 17499-17512

DOI: 10.1039/C8NJ03460E

Mishura A.; Lytvynenko A.; Gavrilenko K.; Baranchikov A.; Grabovaya N.; Kiskin M.; Kolotilov S.

Nanoporous silver foam on a glassy carbon electrode (AgNF/GC) was formed by cathodic deposition of silver from an acidic solution of AgBF4 at high current density. The material can be described (based on results of optical microscopy, SEM, TEM and XRD investigation) as hierarchically (micro/nano) porous matter with ca. 40 nm silver crystals assembled in irregular ca. 70–300 nm thick filaments arranged in a foam-like structure with ca. 20 µm cavities and ca. 7 µm walls. The AgNF surface area was estimated by pseudocapacitance measurement as ca. 12 times higher than the geometrical area. Reduction of bromobenzene and other aryl bromides containing redox-inactive (F-, CH3-, CH3O-) or redox-active (–NO2, –CN and CH3CO-) substituents, as well as alkyl bromides (CF3CHClBr, CF2Br2) on AgNF/GC was studied. The peak potentials of the processes assigned to debromination of the organic halides were less negative (up to +345 mV) than on smooth silver, indicating superior electrocatalytic properties of the nanoporous silver foam. Comparison of the CV peak currents of the processes on AgNF/GC and smooth silver, as well as their changes in cycling in different regimes allowed formation of a few kinds of electrocatalytically active sites on the AgNF surface to be suggested. Electrolysis of 1-bromo-4-fluorobenzene on the AgNF electrode led to fluorobenzene, and less than 1 mg of AgNF revealed performance comparable to 500 mg of smooth silver wire. The results can be utilized for creation of electrochemical sensors as well as for preparative detoxification of halogen-containing persistent organic pollutants

Formation of hierarchically-ordered nanoporous silver


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