Avaliação da eletroatividade de nanopartículas metálicas dispersas em eletrodo impresso frente à eletro-oxidação de metanol utilizando sistema em fluxo

Anodes of direct alcohol fuel cells (DAFC)are composed by Pt nanoparticles (NPs) immobilized on carbon support [1].The activity of synthesized NPs is studied by classic stationary electrochemical measurements(CM), in very cleanenvironment and inert atmosphere. However, in DAFC, the alcohol continuously feeds the anode in an impuresystem in the presence of O2. Here, we propose a flow system to measure the electroactivity of nanoparticles (FSMEN). In FSMEN, the alcohol is continuously carried outto a screen-printed electrode modified with NPs placed at the bottom of a homemade polymeric cell(wall-jet configuration [2]), producing ananodic transient, which is monitored to evaluate the activity. We investigated the activity and stability ofPt NPson carbon (Pt/C), multi-walled carbon nanotubes (Pt/MWCNTs) and graphene nanoribbons (Pt/GNRs) formethanol electrooxidation and the results were compared toCM. Both methods reveal that Pt/GNRs are more activeamongthe catalysts, followed by Pt/MWCNTs and Pt/C (Figs. 1A and 1B), which is in line with previous reports [1]. Differently, FSMEN showsan improvement of eleven times by using Pt/GNRs while the classic experiment reveals three-foldenhancement(Fig. 1A).Comparing the activity at 0,6 V in the range 200-1800s (not shown), CMshowed loss of 24% and 27% of Pt/GNRs and Pt/MWCNTs initial activities, respectively, while FSMEN showed loss of 61% and 80%. The difference found by FSMEN is understood as a consequence of the detachment of NPs from the carbon supports due to continuous flow. Therefore, our method reveals that the activity might be under estimated and the stability overestimated by using CM. Moreover, FSMEN is a promisingmethod to evaluate the activity of NPs due to thelow cost, simple instrumentation and low consumption of fuel.