Design of Low pH Stable and Highly Active (Ti, Zn) Doped RuO2 Electrocatalysts for Electrochemical Water Oxidation

High overpotential, low stability and cost of the electrocatalysts represent significant challenges for oxygen evolution reaction (OER) operating in the acidic medium. In this regard, blending active (usually unstable) and passive (usually not active) components is one of the methods to tackle this challenge. Here, active Zn and passive Ti are blended in Ru-based oxides through co-electrodeposition method. The composition of the electrodes has been optimized by controlling the electrodeposition bath concentration. The surface roughness of the resultant electrode is increased due to introduction of ‘chemical inhomogeneity’ by Ti and ‘structural inhomogeneity’ through Zn.  It has been found that incorporation of Zn and Ti additives increase both activity and stability of electrodes.  The maximum catalytic activity is found in the composition of Ru_0.259Ti_0.736Zn_0.006O_x with a current density of 63mA/cm² at an operating voltage of 1.35V (vs Ag/AgCl). The activity of this electrode is four times higher than electrodeposited RuO₂ and also higher than other possible binary combinations in Ru-electrodes (RuTi, RuZn). The stability of the electrodes among the co-electrodeposited electrodes are found to be in order of co-electrodeposited RuZn<co-electrodeposited RuTi<co-electrodeposited RuTiZn.The increase in catalytic activity of the co-electrodeposited electrodes can be attributed to the combination of lowering of activation energy thereby increasing site activity and increase of available active sites due to promotion of roughness in surface by the Zn and Ti. The increased stability may be attributed to intermixing of additives leading to formation of porous stable surface layer as suggested by impedance spectroscopy.