Unveiling the Electrocatalytic Activity of the GdBa0.5Sr0.5Co2–xCuxO5+δ (x ≥ 1) Oxygen Electrodes for Solid Oxide Cells

The A-site cation-orderedGdBa(0.5)Sr(0.5)Co(2-x )Cu( x )O(5+& delta;) (GBSCC)double perovskites are evaluated regardingthe development of high-performance oxygen electrodes for reversiblesolid oxide cells (rSOCs). The aims are to maximally decrease thecontent of toxic and expensive cobalt by substitution with copperwhile at the same time improving or maintaining the required thermomechanicaland electrocatalytic properties. Studies reveal that compositionswith 1 & LE; x & LE; 1.15 are particularlyinteresting. Their thermal and chemical expansions are decreased,and sufficient transport properties are observed. Complementary densityfunctional theory calculations give deeper insight into oxygen defectformation in the considered materials. Chemical compatibility withLa(0.8)Sr(0.2)Ga(0.8)Mg(0.2)O(3-& delta;) (LSGM) and Ce0.9Gd0.1O2-& delta; (GDC) solid electrolytes is evaluated.It is documented that the GdBa0.5Sr0.5Co0.9Cu1.1O5+& delta; oxygen electrode enablesobtaining very low electrode polarization resistance (R (p)) values of 0.017 & omega; cm(2) at 850 & DEG;Cas well as 0.111 & omega; cm(2) at 700 & DEG;C, which is lowerin comparison to that of GdBa0.5Sr0.5CoCuO5+& delta; (respectively, 0.026 and 0.204 & omega; cm(2)). Systematic distribution of relaxation times analyses allows studiesof the electrocatalytic activity and distinguishing elementary stepsof the electrochemical reaction at different temperatures. The rate-limitingprocess is found to be oxygen atom reduction, while the charge transferat the electrode/electrolyte interface is significantly better withLSGM. The studies also allow elaborating on the catalytic role ofthe Ag current collector as compared with Pt. The electrodes manufacturedusing materials with x = 1 and 1.1 permit reachinghigh power outputs, exceeding 1240 mW cm(-2) at 850 & DEG;C and 1060 mW cm(-2) at 800 & DEG;C, for theLSGM-supported cells, which can also work in the electrolysis mode.