Oxygen Evolution and Reduction Reactions on La0.8Sr0.2CoO3 (001), (110), and (111) Surfaces in an Alkaline Solution

Abstract

The oxygen evolution and reduction properties of La 0.8 Sr 0.2 CoO 3 are characterized using two-dimensional model electrodes with different reaction planes, synthesized on SrTiO 3 single crystal substrates by pulsed laser deposition. Thin-film X-ray diffraction and reflectivity measurements confirm the epitaxial growth of 29-nm-thick La 0.8 Sr 0.2 CoO 3 (001), (110), and (111) films on SrTiO 3 (001), (110), and (111) substrates, respectively. Cyclic voltammetry curves in 1-M KOH aqueous solution indicate that the (110) film has the highest activity for oxygen evolution and reduction reactions. An expansion of the La 0.8 Sr 0.2 CoO 3 lattice is observed after the oxygen reduction process, indicating the formation of oxygen defects, with the highest number of defects being produced in the (110) film. X-ray reflectivity analysis demonstrates the formation of a surface layer on the La 0.8 Sr 0.2 CoO 3 films during electrochemical cycling due to the decomposition of La 0.8 Sr 0.2 CoO 3 . The surface structure constructed at the electrode/electrolyte interface is a crucial factor influencing oxygen evolution and reduction activity of La 0.8 Sr 0.2 CoO 3 .

Perovskite Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Media

“…All Mn-containing perovskites showed catalytic activity but the weak dependence on rotational speed in RDE measurements [127,128] suggests that oxygen is not directly reduced to water on these surfaces, which is in agreement with microkinetic analysis of composite electrodes [97]. LaCoO 3 [60,129] [96,131] showed no activity but could be activated by addition of carbon [96]. Due to the similarity in the chemistry of the Co-based perovskites, the discrepancy is unlikely to be caused by doping of divalent cations and requires further studies.…”

“…However, the chemical, structural, and magnetic properties of the oxides are likely not fully optimized as will be argued in Section 6. In contrast to single crystalline Pt (Figure 3a), the activity of single crystalline perovskite oxides depends weakly on the surface facet (Table 2) in previous reports [63,96,131], so that the most commonly investigated (100) surfaces are compared. The most active composite electrodes [22] are also included for reference.…”

Influence of Surface Orientation on the Catalytic Activities of La0.8Sr0.2CoO3 Crystal Electrodes for Oxygen Reduction and Evolution Reactions

“…Recently, some studies have shown that carbonaceous materials can make electrocatalytic contributions to the ORR in alkaline solutions . In addition, the intrinsic catalytic properties of perovskites themselves were studied by using stationary electrodes of perovskites fabricated by pulsed laser deposition (PLD) . Our group reported, for the first time, the intrinsic electrochemical properties of perovskites as an oxygen electrode through the combined use of PLD‐grown perovskite thin films and rotating disk electrodes (RDEs) : Even La 0.8 Sr 0.2 CoO 3 (LSCO), which is known to be a highly electroconductive perovskite, showed much lower ORR activities than those of the composite electrodes, whereas LSCO exhibited clear OER activities that were as high as those of the composite electrodes.…”

Hydrogen production by alkaline water electrolysis

“…[171][172][173][174][175][176][177] Ir x Ru y Ta z O 2 as an anode electrocatalyst achieved an overall cell voltage of 1.57 V at 1 A cm −2 at 80 °C, with an energy consumption of 3.75 kWh N m −3 H 2 and efficiency of 94%, for a total noble metal loading of less than 2.04 mg cm −2 . 47 However, there are some non-noble, less expensive metals that also present electrocatalytic activity and are being introduced for use in oxygen [178][179][180][181][182][183][184][185] and hydrogen 165,166,[186][187][188][189][190][191] evolution reactions. Additionally, during designing an electrode, it is normally doped or coated with more stable and active layers.…”