Size- and Density-Controllable Fabrication of the Platinum Nanoparticle/ITO Electrode by Pulse Potential Electrodeposition for Ammonia Oxidation

Pulse potential electrodeposition was successfully utilized to electrochemically fabricate platinum (Pt) nanoparticles on indium tin oxide (ITO) conductive glass substrates for catalysis toward ammonia electro-oxidation. The effect of deposition parameters (lower potential E-l, lower potential duration t(l), and upper potential duration t(u)) on the size and number density of Pt nanoparticles was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrocatalytic activity of the Pt nanoparticle/ITO electrode for ammonia oxidation was characterized by the cyclic voltammetry (CV) method. The results showed that lower E-l and longer t(l) accelerate the formation of Pt nuclei while longer t(u) favors the growth of grain size to some extent, as E-l mainly tunes electrochemical overpotential while t(l) and t(u) affect the activation and mass transfer process. By the tuning of the deposition parameters, Pt nanoparticle/ITO electrodes with a polycrystalline nature and 5 nm-scale primary particles, could be easily modified in Pt particle size and number density. Furthermore, the Pt nanoparticle/ITO electrode shows high mass specific catalytic activity (MA) toward ammonia oxidation (1.65 mC g(1)), much higher than that of the commercial Pt/C electrode (0.32 mC g(1)). Additionally, the high catalytic performance results not only from the nanosize effect of Pt nanoparticles, but also from the special morphology formed during the electrodeposition process.