Electrochimica Acta 92 (2013) 31–35 Contents lists available at SciVerse ScienceDirect Electrochimica Acta jou rn al hom epa ge: www.elsevier.com/locate/electacta Formic acid microfluidic fuel cell evaluation in different oxidant conditions A. Déctor a , J.P. Esquivel b,∗ , M.J. González b , M. Guerra-Balcázar c , J. Ledesma-García c , N. Sabaté b , L.G. Arriaga a,∗∗ a Centro de Investigación y Desarrollo en Tecnología Electroquímica, Parque Tecnológico Querétaro Sanfandila, Pedro Escobedo, 76703 Querétaro, Mexico b Instituto de Microelectrónica de Barcelona, IMB-CNM (CSIC), Campus UAB, 08193 Bellaterra, Barcelona, Spain. Tel: +34 935947700 c División de Investigación y Posgrado, Universidad Autónoma de Querétaro, Cerro de las campanas s/n, 76010 Santiago de Querétaro, Mexico a r t i c l e i n f o Article history: Received 17 August 2012 Received in revised form 23 December 2012 Accepted 31 December 2012 Available online 8 January 2013 Keywords: Formic acid electrooxidation Microfluidics fuel cells Dissolved oxygen Air Hydrogen peroxide a b s t r a c t This paper presents the electrochemical evaluation from polarization curves of a microfluidic fuel cell that uses formic acid as fuel and different oxidants (dissolved oxygen, air and hydrogen peroxide), concentrations of fuel and flow rates. The micro-device was constructed by UV-lithography technique and the electrocatalysts consisted in commercial Pd/XC-72 and Pt/C for anode and cathode respectively. The maximum power density achieved was 6.7 mW cm -2 at 0.5 V using 0.5 M HCOOH and dissolved oxygen at 600 L min -1 . © 2013 Elsevier Ltd. All rights reserved. 1. Introduction In recent years microfluidic fuel cells devices have been consid- ered by the scientific community as particularly important in the context of the next generation for on-chip power sources applica- tions [1–5]. Microfluidic fuel cells developed to date are fed by liquid fuels and oxidants under laminar flow regimen. These devices, also called laminar flow-based membraneless fuel cells, operate without a physical barrier to separate the anode and the cathode, which pro- vides an opportunity to overcome the challenges associated with conventional PEM fuel cells. The laminar nature of the flow as well as the type of electrolyte present in the fuel and oxidant streams facilitate the transverse movement of the protons by diffusion from the anode to cathode keeping low Reynolds number [6–8]. Further advantage related to the use of liquid fuels is their higher volumet- ric energy densities compared to gaseous fuels [1,6]. Some fuels frequently used in microfluidic fuel cells are formic acid [9–13], methanol [14,15] and glucose [16–18]. Generally, the oxygen is incorporated into the flow by bubbling in the electrolyte ∗ Corresponding author. ∗∗ Corresponding author. Tel.: +52 442 2116069; fax: +52 442 2116006. E-mail addresses: juanpablo.esquivel@imb-cnm.csic.es (J.P. Esquivel), larriaga@cideteq.mx (L.G. Arriaga). [9,12,15]. However, the reduced oxygen diffusivity (2 × 10 -5 cm 2 /s) in aqueous media and its low concentration (2–4 mM) in liquid medium [22] limit the mass transfer affecting the performance of the device. This limitation can be addressed using liquid oxidants with higher oxygen concentration as vanadium [23,24] or hydro- gen peroxide [20,21,25,26] or by integration of an air-exposed gas diffusion electrode [22,27]. Hydrogen peroxide is liquid at standard temperature and pressure conditions and presents the advantage of having a high oxygen concentration and a high solubility in aqueous media [21,29]. The use of formic acid as fuel in microfluidic fuel cells has con- siderable advantages for portable power applications [9–12]. The electrooxidation of formic acid on Pd catalysts has been extensively studied, e.g. Pd nanoparticles supported on carbon Vulcan XC-72 evaluated in a microfluidic formic acid fuel cell in the presence of dissolved oxygen in 0.5 M H 2 SO 4 as oxidant [12,13]. The following work reports a microfluidic fuel cell composed by microfabricated components that incorporates the same catalytic materials. The improved device design and fabrication techniques result in higher power densities compared with previously reported devices from our group. The present microfabricated device is then used to evaluate the microfluidic fuel cell performance using three con- centrations of formic acid as fuel and three different oxidants (dissolved oxygen, air or hydrogen peroxide). The influence of the oxidant, concentration of fuel and flow rate of reactants on the device performance was evaluated from its polarization curves. 0013-4686/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.12.134