Sol–gel Ru_0.3Sn_0.7O₂ 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 Cl₂ production and the Cl₂ bubble evolution behaviour. For comparison, a state-of-the-art mud-crack commercial Ru_0.3Ti_0.7O₂ 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 TiO_x interlayer is formed between the mud-crack Ru_0.3Sn_0.7O₂ 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 Ru_0.3Sn_0.7O₂ coatings with different surface microstructure are evaluated by means of scanning electrochemical microscopy and microscopic bubble imaging.