Characterization of Nanoporous Gold Supports

For determination of the pore and ligament sizes of the npAu supports as well as the zinc distribution the samples were transferred onto a microscope sample holder with a conductive carbon tape. Micrographs of the samples morphology were acquired with a Supra 40 (Zeiss, Germany) scanning electron microscope operated at 10.0 kV acceleration voltage, 300 pA probe current and 4 mm working distance. The pore and ligament sizes were determined by measuring the diameter of at least 250 pores or ligaments in the obtained SEM images using the program ImageJ. The specific surface area S was calculated from the ligament diameter d according to S = (C/ρd) where C is the porosity factor for npAu with 3.7 and ρ is the gold bulk density of 19.8 g cm⁻³ according to literature.^{40,41 (link)} This method was shown to give values that are in good agreement with both, data from gas adsorption experiments (BET) as well as electrochemical methods (CV).^{40,41 (link)} The amount of immobilized ZnPc as well as the zinc distribution on the surface were determined by energy dispersive X-ray spectroscopy (EDX, Bruker XFlash 6/30).