Surface Changes at Platinized Platinum Based Hydrogen Gas Electrodes Following Use in Highly Saline Aqueous Solutions

Platinized platinum based hydrogen gas electrodes, Pt(Pt)|H2(g)|H+(aq), and silver-silver chloride electrodes, Ag|AgCl|Cl− (aq), make up the Harned cell, without transfer, working in the potentiometric mode at Cl− concentrations and ionic strengths, I, below 0.1 mol kg−1, for assigning primary pH values to reference pH buffer solutions. This work reports on experiments performed at higher I and Cl− solutions up to 0.7 mol kg−1, aiming at addressing seawater conditions with results of equally high quality. In the course of measurements, the occasional occurrence of highly unstable potentials denoted electrode malfunction; Pt metal surfaces observed by SEM/EDS and XRD exhibit strong Ag and Cl peaks corresponding to the presence of AgCl crystals deposited at both surfaces.