Electrocatalytic Reduction Of Nitrate Ions At Bimetallic And Trimetallic Electrodes In A Membrane Reactor

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dc.contributor.authorKoay, Poh Poh
dc.date.accessioned2018-02-02T06:48:37Z
dc.date.available2018-02-02T06:48:37Z
dc.date.issued2017-03
dc.description.abstractThe electrocatalytic reduction of nitrate ions (NO3−) and electrolysis were performed in a neutral medium by using linear sweep voltammetry technique and a sandwich type membrane reactor, MNafionM-X (where, M = Pd-Pt and X = Cu, SnCu). The voltammetric studies were carried out by using various working electrodes such as platinum (Pt), platinum modified copper (Cu-Pt), platinum modified tin (Sn-Pt), platinum modified nickel (Ni-Pt) and platinum modified SnCu-Pt electrodes. Pt electrode shows very little activity towards electrocatalytic of nitrate reduction. When Cu, Sn and Ni particles are deposited on Pt surface, the nitrate reduction ability of Pt was improved. When the Pt surface was covered with promoter metal particles, the hydrogen evolution site was blocked and hence the nitrate reduction process was more effective. Therefore −0.40 to −1.2 V was chosen as the optimal potential range to perform the NRR reaction as to avoid the HER reaction and also the Cl-Cl interaction peaks. The voltammetric results showed that the performances of electrode towards catalytic effect were in the order of Pt < Sn-Pt < Cu-Pt < Ni-Pt < SnCu-Pt. The synergistic effects originated from the combination of Pt, Sn and Cu metals created sufficient nitrate reduction sites. Nitrate and nitrite ions do not affect each other during the course of their reduction at the SnCu-Pt electrode. The kinetic results have been discussed in terms of Tafel slope, exchange current density and order of reaction. All electrodes follow first order kinetics. All electrodes show two electrons transfer at the rate determining step indicating the reduction of nitrate ions to nitrite ions. The electrode was investigated in terms of the influence of anions and cations in the supporting electrolyte. The results for in for influence of anions in the supporting electrolyte show that the reduction of nitrate decreases in the order F- > Cl- > Br- > I-. The results for influence of cations in the supporting electrolyte show that the reduction of nitrate increases in the order of Cs + < K + < Na + < Li +. Results indicated that the reduction of nitrate and its intermediate (NO2−) were greatly enhanced by the addition of copper and tin catalysts which were immobilized on the Pt surface. The controlled current electrolysis experiments showed that 60% of nitrate ions were converted to NO2− and NH4+ by using a PdCu-Pt electrode. The PdCu-Pt catalyst elevated the first step of the consecutive NO3− reduction by converting NO3− into NO2−. But a composite PdSnCu-Pt electrode accelerated both the nitrate and nitrite reduction process yielding 97% of nitrate removal to other non-ionic N-species products. The SEM micrograph shows the Cu and Sn particles have been uniformly deposited on the Pd-Pt membrane. The morphological changes were not visible even after used. The EDX spectrum confirmed that the membrane is a ternary electrode.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/5483
dc.language.isoenen_US
dc.publisherUniversiti Sains Malaysiaen_US
dc.subjectElectrocatalytic reduction of nitrate ions at bimetallicen_US
dc.subjectand trimetallic electrodes in a membrane reactoren_US
dc.titleElectrocatalytic Reduction Of Nitrate Ions At Bimetallic And Trimetallic Electrodes In A Membrane Reactoren_US
dc.typeThesisen_US
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