*Article* **Facile Synthesis of Unsupported Pd Aerogel for High Performance Formic Acid Microfluidic Fuel Cell**

**Alejandra Martínez-Lázaro 1, Luis A. Ramírez-Montoya 2, Janet Ledesma-García 1, Miguel A. Montes-Morán 3, Mayra P. Gurrola 4, J. Angel Menéndez 3, Ana Arenillas 3,\* and Luis G. Arriaga 5,\***


**Abstract:** In this work, unsupported Pd aerogel catalysts were synthesized for the very first time by using microwaves as a heating source followed by a lyophilization drying process and used towards formic acid electro-oxidation in a microfluidic fuel cell. Aerogels were also made by heating in a conventional oven to evaluate the microwave effect during the synthesis process of the unsupported Pd aerogels. The performance of the catalysts obtained by means of microwave heating favored the formic acid electro-oxidation with H2SO4 as the electrolyte. The aerogels' performance as anodic catalysts was carried out in a microfluidic fuel cell, giving power densities of up to 14 mW cm−<sup>2</sup> when using mass loads of only 0.1 mg on a 0.019 cm<sup>2</sup> electrode surface. The power densities of the aerogels obtained by microwave heating gave a performance superior to the resultant aerogel prepared using conventional heating and even better than a commercial Pd/C catalyst.

**Keywords:** unsupported aerogel; microwave heating; microfluidic fuel cell; electro-oxidation
