Preparation of La-Cr Perovskite Coating Using Electrodeposition Method

Abstract

An adhesive LaCrO 3 perovskite coating has been prepared on stainless steel substrate by cathodic electrodeposition from aqueous solution 0.03 M La(CH 3 COO) 3 + 0.03 M CrCl 3 + 0.03 M Na 3 C 6 H 5 O 7 , followed by heat-treatment at 800 • C in air. The electrodeposition of La-Cr coatings has been examined in the solution with pH of 2∼3 at the current density of 1∼5 mA cm −2 . It is shown that the change of pH by even 0.1 can affect obviously the deposition of La-Cr coatings, and increasing the current density will lead to the generation of more cracks in the coatings. A more uniform and compact La-Cr coating can be obtained in the solution with the optimized pH value of 2.7 at the optimized current density of 1 mA cm −2 . The La and Cr deposits change from their metallic states to the hydroxides during electrodeposition, corresponding to the increase in the pH with time. The as-prepared La-Cr coating is rich in La, due to the strong coordination of trivalent chromium with complex agent in the bath. The outward diffusion of Cr from the stainless steel substrate supplies the as-prepared La-rich coating to form LaCrO 3 during heat-treatment. which are capital intensive and difficult for scale production. Electrodeposition of Ln-M coatings from aqueous solutions followed by heat-treatment is an advantageous method for preparing perovskite coatings. [11][12][13][14][15] This method offers a more economical and efficient technique for the fabrication of perovskite coatings. Nevertheless, although the Ln-M coatings have been successful prepared using both anodic and cathodic electrodeposition methods, relevant research is still limited and challenging.Matsumoto et al [11][12][13] conducted a series of research on the anodic electrodeposition of Ln-M (M = Co, Mn) coatings. Their studies indicated that Ln ions did not participate in any oxidation reactions. The incorporation of Ln ions into the M hydroxide/oxide coatings was achieved by enriching the bath with Ln ions and their consequent adsorption. This gives poor control over the Ln contents in the coatings and requires a high concentration of Ln ions for deposition. 15By comparison, cathodic electrodeposition is an inherently superior technique as both Ln and M ions participate in the reactions, leading to facile deposition of Ln and M elements. 14 However, the cathodic electrodeposition of Ln-M coatings still faces some problems. The main obstacle stems from the low equilibrium potentials of Ln ions. Since the equilibrium potentials of Ln ions (Ln 3+ + 3e -→Ln; E 0 = -2.52 ∼-2.25 V SHE ) are much more negative than that of water (2H 2 O + 4e -→2OH -+ H 2 ; E 0 = -0.828 V SHE ), electrolytic decomposition of water appears preferentially.16,17 Fortunately, electrodeposition of Ln elements can be achieved by adding some complex agents to shift their evolution potentials to more positive values. 18,19 Lokhande et al 20 investigated the electrodeposition of La from aqueous solutions on different substrates and found that sodium citrate was a suitable complex agent for L...

Recent Advances in Novel Nanostructuring Methods of Perovskite Electrocatalysts for Energy‐Related Applications

“…The perovskite‐type oxides can also be produced using electrodeposition when coupled with a thermal treatment, usually under air atmosphere, although most of the examples are limited to perovskite thin films deposited onto platinum electrodes, including LaCrO 3 , LaCoO 3 (LCO), and LnMO 3 (Ln = La, Pr, Nd; M = Al, Mn, Fe) . Very recently, Zhang and co‐workers applied electrodeposition to the synthesis of LaCo 0.8 Fe 0.2 O 3 perovskite nanoparticles hybridized with an NF substrate (NF/oLCFO‐Ar) .…”

“…Materials that can be deposited onto these substrates include metals, [108] metal oxides, [109] metal (oxy)hydroxides, [107,110] and metal sulfides, [111] with varying morphologies such as nanowires, [109] nanosheets, [111] and nanofilms. [108] The perovskite-type oxides can also be produced using electrodeposition when coupled with a thermal treatment, usually under air atmosphere, although most of the examples are limited to perovskite thin films deposited onto platinum electrodes, including LaCrO 3 , [112] LaCoO 3 (LCO), [113] and LnMO 3 (Ln = La, Pr, Nd; M = Al, Mn, Fe). [114] Very recently, Zhang and co-workers applied electrodeposition to the synthesis of LaCo 0.8 Fe 0.2 O 3 perovskite nanoparticles hybridized with an NF substrate (NF/oLCFO-Ar).…”

Electrochemical preparation of nano/micron structure transition metal-based catalysts for the oxygen evolution reaction

“…149 Zeng's group fabricated an adhesive LaCrO 3 perovskite coating on stainless steel by cathodic electrodeposition of a La-rich La–Cr coating composed of external La/Cr oxides or hydroxides and inner La–Cr from an aqueous citrate solution, followed by heat treatment in air. 150 With the optimized pH value of 2.7 at the optimized current density of 1 mA cm −2 , a more uniform and compact La–Cr coating was obtained in the solution. The La and Cr deposits changed from their metallic states to hydroxides during electrodeposition.…”