Portal de Periódicos da CAPES

Reduction of Aqueous Ag+ Steered by Electrochemical Plasma: Connecting the Bulk pH Variation with the Reaction Pathways for Hydrated Electrons

2019; Brazilian Chemical Society; Linguagem: Inglês

10.21577/0103-5053.20190020

1678-4790

Ingrid Azevedo Gonçalves, Jairo Barauna, Fernando J. Cunha-Filho, Osvaldo Chiavone‐Filho, Jussier de Oliveira Vitoriano, Clodomiro Alves, Andressa Mota-Lima,

Advanced battery technologies research

Reduction of silver cations followed by nanoparticle (Ag-NPs) synthesis is a model process to understand the reduction mechanism induced by a discharge over an aqueous surface, termed electrochemical plasma.This work aims at studying the silver reduction reaction steered by electrochemical plasma in the presence of other chemically active plasma-related interfaces, namely the plasma-gas and the liquid-gas interfaces.As no other plasma-induced species are able to reduce silver cations, the reduction of silver cations is employed as strategy to selectively detect the presence of hydrated electrons ( ).The results demonstrate that the global rise of pH (increase in the content of OH -), observed for discharge in the helium gas phase, occurs in connection with the silver reduction, which is interpreted as a vivid experimental evidence of the second-order recombination reaction of the (2e - aq + 2H 2 O → H 2 + 2OH -).On the other hand, the global decrease of pH (increase in the content of H + ) observed for discharge in mixed oxygen and nitrogen gas phase, is an event primarily driven by the Birkeland-Eyde process, and it is concomitant but spatially distinct from the electron injection.The acidification interferes in the NP formation, as NPs promptly dissolve in presence of HNO 3 .Only in complete suppression of the acidification, an experimental evidence of the reaction pathways for hydrated electron could be captured: is competitively consumed through a scavenger-like reaction (reduction of silver cations in this work) and through the second-order recombination reactions of the .The kinetic model proposed in this work further corroborates this interpretation.