Investigation of Electrochemical Oxidation of Methanol at a Carbon Paste Electrode Modified with Ni(II)‐BS Complex and Reduced Graphene Oxide Nano Sheets

Abstract

In the present research, the electro oxidation of methanol was investigated by different electrochemical methods at a carbon paste electrode (CPE) modified with bis(salicylaldehyde)‐nickel(II)‐dihydrate complex (Ni(II)‐BS) and reduced graphene oxide (RGO) (which named Ni(II)‐BS/RGO/CPE) in an alkaline solution. This modified electrode showed very efficient activity for oxidation of methanol. It was found that methanol was oxidized by NiOOH groups generated by further electrochemical oxidation of nickel (II) hydroxide on the surface of the modified electrode. The rate constant and electron transfer coefficient were calculated to be 2.18 s−1 and 0.4, respectively. The anodic peak currents revealed a linear dependency with the square root of scan rate. This behaviour is the characteristic of a diffusion controlled process, so the diffusion coefficient of methanol was found to be 1.16×10−5 cm2 s−1 and the number of transferred electron was calculated to be 1. Moreover, differential pulse voltammetry (DPV) investigations showed that the peak current values were proportional to the concentration of methanol in two linear ranges. The obtained linear ranges were from 0.5 to 100.0 µM (R2=0.991) and 400.0 to 1300.0 µM (R2=0.992), and the detection limit was found to be 0.19 µM for methanol determination. Generally, the Ni(II)‐BS/RGO/CPE sensor was used for determination of methanol in an industrial ethanol solution containing 4.0 % methanol.

Investigation of Methanol Behavior at the Designed Electrochemical Sensor based on Ni(II) Complex and Graphene Nanosheets

“…Using the slope of the I vs. t −1/2 plot, the average value of the diffusion coefficient for methanol was as 2.85 × 10 −5 cm 2 /s (Figure , inset (b)). These observations show that the calculated value of the diffusion coefficient of methanol is comparable with other reported values in the literature …”

“…The detection limit based on 3 sb/m was calculated as 0.68 μM. Table compares the efficiency of the fabricated electrochemical sensor to other reported sensors for the determination of methanol . From the obtained results for the Ni(II)‐MHP/RGO/CPE sensor for methanol determination, the constructed sensor is seen to have a comparable linear range and detection limit with those of other sensors.…”

Desenvolvimento de eletrodo de pasta de carbono modificado para a quantificação do teor alcoólico em amostras de uísque

“…Já foram usados diversos tipos de modificadores para promover um aumento na atividade eletrocatalítica para a oxidação dos álcoois sendo os mais empregados para este fim materiais biológicos, nanofios metálicos, complexos, óxidos e etc. [52,[70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87][88] .…”

“…Mais recentemente, foram publicados trabalhos envolvendo o uso de eletrodos modificados com nanofios metálicos, nanotubos de carbono, complexos de níquel e óxidos de cromo, níquel e grafeno reduzido que mostraram excelente atividade eletrocatalítica na oxidação de álcoois obtendo baixos limites de detecção e quantificação [52,[75][76][77][78][79][80][81][82][83][84][85][86][87][88] .…”

“…Em estudos realizados por Roslonek e Taraszewska [89] e Bae et al [90] para a análise da atividade eletrocatalítica promovida pelo complexo de níquel-tetraazamacrocíclico em relação às oxidações dos álcoois e do ácido L-ascórbico respectivamente, foi identificado um melhor desempenho do complexo estudado em comparação com o NiOOH, devido ao fato do complexo ter apresentado um sobrepotencial menor (0,1 V) e uma corrente de oxidação aproximadamente cinco vezes maior que os evidenciados pelo NiOOH. Outros estudos reportados também envolvendo o uso de outros complexos de níquel como modificadores em eletrodos que favoreceram a eletro-oxidação de álcoois foram realizados por Golabi e Nozad [91] , Ciszewski e Milczarek [92] , Golikand et al [75] , Golikand et al [93] , Cardoso et al [76] e Mousavi et al [82] .…”