Electrodeposition of Cd on supported Ag nanoparticles and film, and their assessment as electrocatalyst material for nitrate reduction

AMBRUSI, R.E.; SILVANA G. GARCÍA

Darmstadt

Congreso; Materials Science and Engineering European Congress (MSE 2018); 2018

German Materials Society

The contamination of water by nitrate ions hasbecome a growing problem worldwide due to the use of nitrogen fertilizers andthe inadequate treatment of wastewater. The electrochemical method of catalyticreduction of nitrate offers an alternative in the detection and remediationareas of nitrate-polluted groundwaters. In this method, the electrode areaformed by combination of different metals [1, 2] becomes important as itincreases the reaction rate of the process. Another way could be themodification of the substrate with an adsorbed submonolayer of another metal,through the UnderPotential Deposition (UPD) phenomenon [3]. On the other hand,bimetallic nanoparticles have attracted great attention, because theirproperties are better than those of monometallic counterparts. These propertiesincrease their function and application in many fields, includingelectrocatalysis. In this work we compare different electrode surfaces to be usedas potential catalysts: single Ag crystals, supported Ag films andnanoparticles, modified with UPD Cd deposits. The silver deposits are generatedby potentiostatic pulses on a highly ordered pyrolytic graphite (HOPG)substrate. In this study, conventional electrochemical and characterizationtechniques (SPM, SEM, XPS) are used. The electrocatalytic effect of thenanostructured surfaces is analyzed.The voltammetric results indicated that theformation of underpotentially deposited Cd on Ag particles follows a behaviordifferent from that observed for single crystal Ag electrodes [4]. The behaviorof the Cd UPD on a modified Ag film/HOPG substrate is similar to that obtainedwith massive Ag substrates, indicating that the Cd adsorption occurs on HOPGpractically covered with Ag. The voltammetric results of the systemCd/Ag(NPs)/HOPG, involved only the formation of a Cd UPD monolayer on Ag (NPs),and an increase in current density prior to this process related to thepresence of Cd expanded structures. The morphology images showed similar sizedAg particles distributed preferably over the step edges of the HOPG. Nonoticeable morphological changes were observed on the surface after thesubsequent deposition of Cd, indicating the formation of Cd-Ag core-shell structures.The modified electrodes were analyzed by cyclic voltammetry in a solutioncontaining different concentrations of nitrate ions. A higher reduction currentwas verified for longer polarization times used in Cd deposition on supportedAg(NPs).