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Electrodeposition of Pt nanoparticles under potentiostatic conditions was performed on several types of carbon electrode supports: a commercial macroporous carbon (which can be considered as a three-dimensional electrode), glassy carbon, graphite and conducting polymers (polyaniline and poly-o-aminophenol). The platinum nanoparticles were obtained by different Potential Step Deposition (PSD) methods in 5 mM H 2 PtCl 6 + 0.5 M H 2 SO 4 aqueous solutions. The effect of the final potential, time and number of steps on the quantity, distribution and size of the platinum nanoparticles deposited on the supports was analysed. The mechanism of the electrochemical deposition of platinum was studied by applying theoretical models found in the literature, being the progressive nucleation mechanism the most consistent with our results. In addition, the chemical state and morphology of the electrodeposited materials The prepared composites have been tested for the electro-oxidation of methanol. 2.-EXPERIMENTAL Preparation of the supportsDifferent carbon materials have been used to prepare the working electrodes for the platinum electrodeposition: macroporous carbon disc, glassy carbon and graphite.The macroporous carbon discs, which were cut from a macroporous carbon sheet (thickness = 0.3 mm, mean pore size 0.7 µm, exposed geometric area 2.91 cm 2 )provided by Poco Graphite (DFP-1) were washed in an ultrasonic bath with distilled water at room temperature for 30 minutes. The graphite (Ellor+35) and glassy carbon (CV25) were rods of 0.3 cm in diameter from Carbone Lorraine.In all cases, the materials were first treated with sandpaper, and were then polished with two different diamond suspensions (particle sizes 1 and 0.25 µm, respectively), and finally washed in an ultrasonic bath with ultrapure water for 5 minutes.The conducting polymers layers were electrochemically deposited on glassy carbon by cyclic voltammetry between 0.06 and 1.10V from a 0.1 M aniline or o -5 aminofenol in a supporting electrolyte of 0.5 M H 2 SO 4 at a scan rate of 50 mV s -1 .Although different expressions can be found for film thickness determination in literature, an EQCM experiment [27] was used to calculate film thickness from polymer peak voltammetric charge. Platinum electrodepositionThe electrodeposition of platinum particles on the different electrodes was performed in a conventional electrochemical cell of three electrodes at room temperature. All the reagents used were of analytical grade, and these and other materials were used without f urther purification. An EG&G potentiostat/galvanostat model 263A controlled by the program POWER SUITE was employed, so the values of current and time were monitored by a computer. For all the experiments the counterelectrode was a platinum wire. The reference electrode was a reversible hydrogen electrode (RHE), immersed in 0.5M H 2 SO 4 solution, which was connected to the working electrode compartment by a Luggin capillary.All solutions were prepared with high-purity water (resistivity =18 MΩ·...

Films of conducting polymers can be oxidized and reduced in a reversible way. Any intermediate oxidation state determines an electrochemical equilibrium. Chemical or physical variables acting on the film may modify the equilibrium potential, so that the film acts as a sensor of the variable. The working potential of polypyrrole/DBSA (Dodecylbenzenesulfonic acid) films, oxidized or reduced under constant currents, changes as a function of the working conditions: electrolyte concentration, temperature or mechanical stress. During oxidation, the reactive material is a sensor of the ambient, the consumed electrical energy being the sensing magnitude. Devices based on any of the electrochemical properties of conducting polymers must act simultaneously as sensors of the working conditions. Artificial muscles, as electrochemical actuators constituted by reactive materials, respond to the ambient conditions during actuation. In this way, they can be used as actuators, sensing the surrounding conditions during actuation. Actuating and sensing signals are simultaneously included by the same two connecting wires.

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