Synthesis of AuNi-N doped of Graphene quantum dots as efficient electrocatalyst in formate-hydrogen peroxide fuel cell

In this study, the effects of Au, Ni as alloy materials and NGQD, as catalyst supports on the performance of the synthesized AuNi-NGQD as anodic catalysts towards formate oxidation and in direct formate-hydrogen peroxide fuel cell were investigated. The three electrode results showed that between different amounts presence of Ni and Au the best performance is related to the synthesized Au۱Ni۱-NGQD which is enhanced the electrocatalytic activity. The results of Direct Formate Hydrogen Peroxide Fuel Cell (DFHPFC) were also in good compartment with three electrode investigations. The obtained power density for Au۱Ni۱-NGQD was ۱۴.۲۳mW cm-۲.With the increasing worldwide need for energy, there is a compelling need to find clean, high-energy-density power sources that are both sustainable and cost-effective. Due to their high energy and power density, low operating temperature, simplicity, low environmental pollution, and ease of manufacture, storage, and distribution, direct liquid fuel cells (DLFCs) are highly promising energy generating devices for portable and stationary applications ۱-۳. Because of the following advantages, direct formate fuel cells (DFFCs) are viewed as an alternative energy-conversion device: (a) Formate is made by converting CO۲ photo electrochemically in a carbon cycle into a fuel cell, and it is conveniently stored and transported ۴ , (b) its oxidation kinetics in alkaline solutions is rapid ۵, c)its toxicity for users is lower ۵. (d) its theoretical cell voltage (۱.۴۵ V) is higher than that of the ones reported for methanol (۱.۲۱ V) , ethanol (۱.۱۴ V) and ethylene glycol (۱.۰۹ V) , (۵) in a DFFC the electron transfer and the current efficiency are higher than that of alcohol-based DLFCs which may be related to completely oxidation of formate to H۲O and CO۲ ۲, ۶.This electrocatalyst was synthesized using nitrogen-doped graphene quantum dots as catalyst support by a two-step reduction method. Simultaneous reduction by sodium borohydride was used to synthesize Ni nanoparticles on NGQD. At first, ۱۸۰ mg of NGQD was dispersed in ۱۵ ml of distilled water in an ultrasonic bath, then ۵ ml of NiCl۲ solution and ۵ ml of NaAuCl۴ solution were added dropwise to NGQD solution, and then sodium borohydride was used to reduce metal ions at ۸۰ ° C for ۲ hours. After stirring for ۲۴ hours, the obtained participate washed, dried, and collected ۷-۸. To prepare the desired inks, ۵ mg of graphene quantum dot doped with nitrogen-containing nickel and gold nanoparticles in different portions were mixed with distilled water, isopropyl alcohol and ۱۰۰ μl of Nafion solution as a binder, and ۵ μl of catalytic ink was placed on a glass carbon electrode with an area of ۰.۱۲۵۱۲ cm۲ as the working electrode. In addition, platinum and mercury/mercury oxide electrodes (MOE) were used as auxiliary and a reference electrode۹. The fuel cell system includes stainless steel end plates, flow collectors made of gold-plated stainless steel, and graphite plates with an active surface area of ۳.۲ cm۲ with spiral grooves with a depth of ۱ mm. A false load device was also used in galvanostat mode to record polarization data. The method is that there is a resistor or consumer in the path of the cell in each specific current, and by using a voltmeter located at both ends of the cell, the potential can be recorded in that current and thus Drawn IV and IP diagrams The cyclic voltammetry curves of Au۱Ni۱-NGQD, Au۱Ni۳-NGQD, Au۳Ni۱-NGQD in NaOH ۱ M and ۰.۵ M formate was compared together. The results show that among the three catalysts synthesized with different ratios of Au: Ni, the ratio of ۱:۱ has the best catalytic performance compared to the oxidation of formate. In other words, NGQD-۱Ni۱Au catalyst has a higher oxidation current density and a more negative oxidation potential than the other two catalysts. After achieving appropriate fuel (۱ M) and oxidant (۲ M) concentrations, the influence of anodic electrocatalyst (Au۱Ni۱-NGQD) on the performance of format fuel cell were compared at ۳۰-۶۰ oC, as shown in Figure ۱a,b. Increasing the operating temperature increases the power density due to improving the diffusion and mass transfer process of Formate and H۲O۲, increasing the kinetics of the formate oxidation reaction as well as reduction of hydrogen peroxide, reducing the viscosity, and increasing the catholyte and anolyte conductivity.Although the operational power density of this project is low, but a general improvement can be seen compared to the other work reported in the literatures

کلیدواژه ها:

Alloy nanoparticles ، NGQD ، Formate oxidation ، Direct formate-hydrogen peroxide fuel cell