An asymmetric cell based on a proton conductor, BaZr(0.1)Ce(0.7)Y(0.1)Yb(0.1)O(3-δ) (BZCYYb), with a well-defined patterned Pt electrode was prepared to study the kinetics and mechanism of the hydrogen oxidation reaction under typical conditions for fuel cell operation and hydrogen separation, including operating temperature and hydrogen partial pressure. Steady-state polarization curves were carefully analyzed to determine the apparent exchange current density, limiting current density, and charge transfer coefficients. The empirical reaction order, as estimated from the dependence of electrode polarization (R(p)) and exchange current density on the partial pressure of hydrogen (P(H(2))), varied from 0.55 to 0.71. The results indicate that hydrogen dissociation contributes the most to the rate-limiting step of the hydrogen oxidation reaction taking place at the Pt-BZCYYb interface. At high current densities, surface diffusion of electroactive species appears to contribute to the rate-limiting step as well.