Hydrogen oxidation at metal–ceria boundary by electrical conductivity relaxation method

•H2 oxidation is studied using ECR technique by increasing pH2.•H2 oxidation is remarkably improved by introducing Pt particles to SDC surfaces.•The catalytic activity increases almost linearly with Pt–SDC–gas boundary length.•The contribution of H2 oxidation from the SDC–gas interface is as small as 4.3%.

Electrical conductivity relaxation (ECR) method is utilized to determine H2 oxidation process on Sm0.2Ce0.8O1.9 (SDC) with scattered Pt or Au particles by increasing the H2 partial pressure in the gas stream. For SDC with Au particles, the reaction occurs only at the SDC–gas interface. When Pt is introduced, the surface exchange kinetics can be remarkably improved whereas the contribution from the ceria–gas interface can be as small as 4.3%. The improvement increases linearly with the Pt–SDC boundary length, demonstrating that H2 oxidation pathway is dominated by the Pt–SDC–gas three-phase boundaries.

Graphical abstractHydrogen oxidation on samaria-doped ceria (SDC) with scattered Pt particles is studied with the electrical conductivity relaxation method. A new coefficient, kPt, is introduced to show the enhanced reaction kinetics. kPt increases almost linearly with the SDC–Pt boundary length, demonstrating that H2 oxidation pathway is dominated by the Pt–SDC–gas three-phase boundaries.Figure optionsDownload full-size imageDownload as PowerPoint slide