Surficial reconstruction in bimetallic oxide SrCoO <sub> <i>x</i> </sub> through Ce-doping for improved corrosion resistance during electrocatalytic oxygen evolution reaction in simulated alkaline saline water
Mohammed Misbah Uddin, Bilal Masood Pirzada, Faisal Rasool, Dalaver H. Anjum, Gareth J. Price, Ahsanulhaq Qurashi
Abstract
Transition metal based bimetallic oxides are good candidates for electrocatalytic oxygen evolution owing to their variable oxidation states, synergistic effects, good conductivity, convincing electrochemical stability, and low cost. However, these materials are highly susceptible to corrosion during saline seawater electrolysis. This work, for the first time, highlights the role of cerium (Ce) doping in bimetallic strontium cobalt oxide (SrCoOx) electrocatalyst for electrochemically stable and corrosion-resistant oxygen evolution reaction (OER) in simulated saline water. The experimental results reveal that 0.5% Ce-doped 5% SrCoOx has the best corrosion resistant ability with respect to the undoped SrCoOx and various other Ce-doped samples. The growth of CeO2 nanoparticles and the generation of CeOx passivation layer through Ce doping were supposed to block the corrosive ions on the surface, thereby hindering chlorine evolution reaction (CER). The Ce3+ ions doped inside the SrCoOx lattice created multiple defects and vacancies which sacrificially facilitate the OER while mitigating the CER. The suppression of corrosive reactions was indicated through low corrosion current (−1.10 μA·cm−2) and high corrosion potential (0.90 V vs. RHE) values suggesting slowest corrosion rate and least tendency towards CER in 0.5% Ce-doped 5% SrCoOx. Consequently, it demonstrated the least Tafel slope of 81.7 mV·dec−1 in saline OER electrolysis with respect to the 121.0 mV·dec−1 was obtained for undoped 5% SrCoOx. Moreover, the electrochemical stability demonstrated in chronoamperometric OER for 45 h and the cyclic voltammetry (500 cycles) confirmed that 0.5% Ce-doped SrCoOx electrocatalyst possesses enhanced anticorrosive properties, which was further supported by post-use linear sweep voltammetry, cyclic voltammetry, and X-ray diffraction analyses. Linear polarization resistance study was also employed on the seawater sample, collected locally, to assess the validity of the present work in real marine systems. In view of the observed results, this work can open an alternate pathway to investigate various transition metal oxide systems as potential corrosion resistant electrocatalysts for seawater.