Modified Glassy Carbon Rotating Disk Electrode for Determination of Heterogeneous Reaction Rate Constant of H₂O₂ Decomposition

Abstract

[a] 1IntroductionThed ecomposition of H 2 O 2 (r 2 in Figure 1) is aw ellknown reactionw hich is employed in different processes. Thep roduct of this reaction,O 2 ,c an be either used as monopropellant or as oxidizer in bipropellant engines such as satellitea ttitude controla nd orbit insertion maneuvers [1,2].A lso,t he decomposition of H 2 O 2 is used as ap art of advanced oxidation processes to produce hydroxylr adicals for treatment of hazardous industrial wastewaters [3,4].I ti sa lso an important reaction affecting the efficiencyo fd ifferent types of fuel cells.Hydrogen peroxide may be produced as an intermediate product in fuel cells using O 2 as the oxidant, and as such it attackst he electrolyte membrane in the polymer electrolyte fuel cells resulting in the mechanical failure of the membrane [5,6].M oreover, H 2 O 2 formation is as erious concern resultingi nar eduction of the activity of Ptbased catalystst oward oxygenr eduction reaction [ 7].I ts decomposition is ad esirable reactioni ns uch fuel cells not only because it gets eliminated,b ut also because it recycles O 2 for reduction. On the other hand, the decomposition of H 2 O 2 is an undesirable reaction when H 2 O 2 is used as the oxidant. Fori nstance,t he formationo fg as bubbles in membraneless microfluidic fuel cells causes crossover and even blockage of the fluidchannel [8].Examples of different catalysts which have been investigatedf or the decomposition of H 2 O 2 include noble metal catalysts such as gold nanoparticles supported on KNbO 3 microcubes [9],n on-noble metal compoundss uch as manganese oxides [10],a sw ell as non-metal catalysts such as multi-walled carbonn anotubes [11].R ecently,i t has been shown that nitrogen doped graphene can catalyse both H 2 O 2 decomposition and reduction reactions [12].N -doped graphene is an ew structure of carbon based catalysts with nitrogen atoms decoratedo nt he honeycomb lattice.Theh eterogeneous reaction rate constant of H 2 O 2 decomposition, k A ,b ased on the surface area of catalystc an be used to compare the intrinsic catalytic activities of different catalysts towardH 2 O 2 decomposition.I no rder to determine k A ,t he concentrationo fH 2 O 2 (c)i sg enerally monitored versus time in as uspension containing ak nown amount of catalyst [13,14].T he heterogeneous reactionr ate constant based on the volumeo ft he suspension, k V ,i st hen determined from the slopeo fl n(c)v ersus time assuming that the reactionf ollows af irst order reaction. Subsequently, k V is converted to k A by using the specific surface area (A), the mass of catalysts uspended in the solution( m), and the suspensionv olume( V):Gasometry and gold rotating diske lectrode( RDE) are two conventionalm ethods employed to measure the H 2 O 2 concentration [13][14][15].I nt he former method, the volume of O 2 produced in the processi su sed to determine H 2 O 2 concentration. In the latter method, the H 2 O 2 concentration is measured from the oxidation of H 2 O 2 on ag old electrode by using the Levich equation. Iodome...