Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements

In recent years, operando/in situ X-ray absorption spectroscopy (XAS) has become an important tool in the electrocatalysis community. However, high catalyst loadings often required to acquire XA-spectra with a satisfactory signal-to-noise ratio frequently imply use of thick layers (CLs) large ion- and mass-transport limitations. To shed light on impact this variable spectro-electrochemical results, study we investigate Pd-hydride formation carbon-supported Pd-nanoparticles (Pd/C) unsupported Pd-aerogel similar Pd surface areas but drastically different morphologies electrode packing densities. Our XAS rotating disk (RDE) measurements unveil that CL-thickness largely determines hydride trends inferred from experiments, therewith calling for minimization such experiments complementary thin-film control measurements.