SURFACE IMPEDANCE TECHNIQUE

AN IN SITU SURFACE CHARACTERIZATION TECHNIQUE IS DEVELOPED TO EVALUATE ELECTROCATALYTIC MATERIALS. THE TECHNIQUE UTILIZES THE PROPAGATION OF HIGH FREQUENCY SURFACE ELECTROMAGNETIC WAVES (SEW) ALONG, RATHER THAN PERPENDICULAR TO, THE ELECTROCATALYST SURFACE. ELECTRON SCATTERING FROM VARIOUS SURFACE PHASES OF THE ELECTROCATALYST (SURFACE OXIDES, HYDRIDES, AND ADSORBATES) ATTENUATE THE SEW AS IT PROPAGATES ALONG THE SURFACE. CALCULATION OF A TRANSFER FUNCTION FOR THE INPUT AND ATTENUATED SEW PROVIDES A FREQUENCY DEPENDENT SURFACE IMPEDANCE. IN A REFINEMENT OF THE SEW IMPEDANCE TECHNIQUE, CROSS POWER AND FAST FOURIER TRANSFORM FUNCTIONS ARE USED TO CALCULATE THE SIMULTANEOUS SURFACE IMPEDANCE RESPONSE TO A MULTIPLE FREQUENCY INPUT SIGNAL. THIS APPROACH ALLOWS THE RAPID EXAMINATION OF A WIDE FREQUENCY SPECTRUM OF SURFACE IMPEDANCE FEATURES ASSOCIATED WITH THE ELECTROCATALYST STABILITY AND SURFACE PHASES IMPORTANT TO EFFICIENT ELECTROCATALYSIS.