2.3.3. Stability Performance

The stability performance was carried out by a chronoamperometry (CA) technique at 0.3 V vs. RHE for 24 h at nitrogen atmosphere.

#### 2.3.4. Evaluation of the Microfluidic Fuel Cell System

The description of the MFC used for these experiments has been previously reported [27]. Both the anode and cathode were Pd aerogel samples deposited on Toray carbon paper-060 (TCP) with a transversal area of 0.02 cm2. The electrocatalyst loading was 0.1 mg for both electrodes. Linear sweep voltammetry (LSV) was performed by injecting 0.5 M HCOOH with H2SO4 as the electrolyte in the anode with the evaluated catalyst; and 0.5 M H2SO4 in the cathode with commercial Pt/C as previous studies reported its best performance [19]. A flow rate of 200 μL min−<sup>1</sup> was used in the test, i.e., Figure 2.

**Figure 2.** Microfluidic system for formic acid electro-oxidation.
