Sustainable energy production is necessary for the next generation. Therefore, it is important to develop/improve a new series of energy technologies that are clean and efficient. A major interest is given to low-temperature fuel cells as an energy conversion device for different applications such as portable devices and electric vehicles. Formic acid is being analyzed and considered to be one of the most promising fuels that could replace methanol in direct liquid fuel cells for portable power applications. The electro-oxidation of formic acid takes place through a dual reaction pathway, dehydrogenation (direct pathway) and dehydration (indirect pathway). In the indirect pathway, a strongly adsorbed CO is produced which blocks the surface, while in the direct pathway CO₂ is directly produced. As the direct pathway requires fewer surface atoms than the indirect pathway,¹ one of the strategies to enhance the catalytic activity and stability of the catalyst is to modify its surface with ad-atmos² or adsorbed species, making the direct pathway more favorable (third body or ensemble effect).³

References:

1. M. Neurock, M. Janik, and A. Wieckowski, Faraday Discuss., 140, 363–378 (2008).
2. A. Ferre-Vilaplana, J. V. Perales-Rondon, J. M. Feliu, and E. Herrero, Acs Catal., 5, 645–654 (2015).
3. E. Leiva, T. Iwasita, E. Herrero, and J. M. Feliu, Langmuir, 13, 6287–6293 (2002).

In this work, the influence of using a blend of ethanol (EtOH) and formic acid (FA) on the catalytic activity of Pd towards the formic acid oxidation is explored in 0.1 M H₂SO₄ at room temperature, using a commercial 40% Pd/C catalyst. It is known that Pd is inactive towards EtOH oxidation and very active towards FA oxidation, and hence the ethanol oxidation contribution in the case of the blend is neglected. It was found that with increasing the ethanol concentration the direct pathway becomes more favorable as indicated by the ratio between peak currents of the direct and indirect pathways in the forward scan.