**4. Conclusions**

The use of microwave heating during the synthesis, followed by lyophilization as the drying step, renders Pd aerogels with a particle size smaller than 5 nm in anchored chains. Furthermore, Pd0 species are generated in a greater proportion when microwave heating is used during the synthesis. These facts demonstrate that the sample obtained by microwave heating presents a much higher electrochemical active surface area, thus favoring the formic acid electro-oxidation reaction. The PdA-MMT sample showed a threetimes superior performance in a microfluidic fuel cell than a commercial Pd/C catalyst, reaching current densities of up to 118.3 mA cm<sup>−</sup>2.

This result shows that the innovative synthesis route presented in this work, using microwave heating for the synthesis process, leads to the production of very competitive aerogels to be used as electrocatalysts.

**Author Contributions:** Conceptualization, L.G.A. and J.L.-G.; methodology, A.A. and L.A.R.-M.; formal analysis, A.M.-L.; resources, L.G.A., J.A.M. and A.A.; writing—original draft preparation, A.M.-L. and L.A.R.-M.; writing—review and editing, L.G.A., M.A.M.-M.; J.L.-G., M.P.G. and A.A.; supervision, L.G.A. and A.A. All authors have read and agreed to the published version of the manuscript.

**Funding:** Mexican Council for Science and Technology (CONACYT) through project Ciencia de Frontera Grant no. 845132 and estancia Sabatica Conacyt 2021-2. Grant PID2020-113001RB-I00 funded by MCIN/AEI/ 10.13039/501100011033 and by the European Union NextGenerationEU/PRTR; Grant PCI2020-112039 funded by MCIN/AEI/ 10.13039/501100011033 and by the European Union NextGenerationEU/PRTR.

**Conflicts of Interest:** The authors declare no conflict of interest.

## **References**

