Microstructural impact of anodic coatings on the electrochemical chlorine evolution reaction

Sol-gel Ru0.3Sn0.7O2 electrode coatings with crack-free and mud-crack surface morphology deposited onto a Ti-substrate are prepared for a comparative investigation of the microstructural effect on the electrochemical activity for Cl-2 production and the Cl-2 bubble evolution behaviour. For comparison, a state-of-the-art mud-crack commercial Ru0.3Ti0.7O2 coating is used. The compact coating is potentially durable over a long term compared to the mud-crack coating due to the reduced penetration of the electrolyte. Ti L-edge X-ray absorption spectroscopy confirms that a TiOx interlayer is formed between the mud-crack Ru0.3Sn0.7O2 coating and the underlying Ti-substrate due to the attack of the electrolyte. Meanwhile, the compact coating shows enhanced activity in comparison to the commercial coating, benefiting from the nanoparticle-nanoporosity architecture. The dependence of the overall electrode polarization behaviour on the local activity and the bubble evolution behaviour for the Ru0.3Sn0.7O2 coatings with different surface microstructure are evaluated by means of scanning electrochemical microscopy and microscopic bubble imaging.