General modeling and experimental observation of size dependence surface activity on the example of Pt nano-particles in electrochemical CO gas sensors

[Display omitted] •Optimization of EPD parameters such as applied voltage, time, and media for fabrication of Carbon electrode including Pt NPs.•Development of EGS (Electrochemical Gas Sensor) for CO gas detection.•Development of general thermodynamics model for estimation of surface activity at nano-scale.•Adequate agreements between results of sensor and computation outcome. In one of our recent published work [Ghashghaie S., et al. Materials Letters, 2015. 141: p. 23–26.], we reported a successful electrophoretic deposition (EPD) of Pt/C on a non-conductive PTFE membrane to produce carbon electrode for CO electrochemical gas sensors (EGS). In the present work, the effect of deposition parameters such as applied field, time and different media on the performance of CO-EGS have been evaluated. The performance of such EGS showed that the combination of ethanol and mixed acetone-isopropanol as media, 50 V applied voltage and 5 min deposition time provides the best EPD parameters. Different experimental depositions have been investigated which leaded us to study the effect of particle size on surface activity of applied catalyst. Moreover, a generalized nano-thermodynamics model was developed to study the size and shape dependency of activity of nano-particles (NPs) as catalyst materials. In this model, in addition to surface-to-volume ratio of catalyst, the effect of surface energy of NPs has been considered. The results of our experiments have been confirmed adequately with proposed model. The introduced model can be applied generally for all physico-chemical reactions involving nano-sized catalyst and particles.