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CN-121976271-A - SOEC metal connector Mn-Co coating and preparation method and application thereof

CN121976271ACN 121976271 ACN121976271 ACN 121976271ACN-121976271-A

Abstract

The invention relates to an Mn-Co coating of an SOEC metal connector, a preparation method and application thereof, belonging to the technical field of solid oxide electrolytic cells. The preparation method comprises the steps of firstly preprocessing a matrix, and constructing an Mn-Co spinel coating on the surface of a metal connector in situ by adopting an in-situ preparation process combining step electroplating and subsequent heat treatment. The coating has good oxidation resistance and low specific surface resistance, and can remarkably prolong the high-temperature service life of the connector.

Inventors

  • NI HONGFEI

Assignees

  • 常州格睿克斯能源科技有限公司

Dates

Publication Date
20260505
Application Date
20251230

Claims (6)

  1. 1. A method for preparing an Mn-Co coating of an SOEC metal connector in situ is characterized by comprising the following steps: s1, substrate pretreatment: Selecting ferrite stainless steel as a metal connector matrix material (sample), and sequentially carrying out mechanical grinding and polishing treatment on the sample; Placing the treated sample in an alkaline solution or an acetone solution for ultrasonic cleaning for 10-20 minutes to thoroughly remove oil stains and impurities on the surface, wherein the alkaline solution is an aqueous solution containing 50-80 g/L sodium hydroxide (NaOH), and the operation temperature is maintained at 30-50 ℃; Sequentially carrying out ultrasonic cleaning for 5-10 minutes by deionized water and absolute ethyl alcohol for multiple times, and then placing in a drying environment for standby; Finally, immersing and activating the sample in an acidic solution for 1-3 minutes, wherein the acidic solution is a hydrochloric acid solution obtained by mixing 90% of concentrated hydrochloric acid and deionized water according to the volume ratio of (10-20): 100 or a sulfuric acid solution obtained by mixing 98% of concentrated sulfuric acid and deionized water according to the volume ratio of (10-15): 100, so as to obtain a pretreated metal connector matrix; S2, electroplating a cobalt transition layer: taking the metal connector matrix pretreated in the step S1 as a cathode, and suspending in cobalt electroplating solution; The basic composition and concentration range of the cobalt electroplating solution are that cobalt sulfate (CoSO 4 ·7H 2 O) is 200-400 g/L, cobalt chloride (CoCl 2 ·6H 2 O) is 30-60 g/L, and boric acid (H 3 BO 3 ) serving as a pH buffer is 25-40 g/L; The pH of the electroplating solution is maintained within the range of 3.5-4.5 by using dilute sulfuric acid (H 2 SO 4 ), and the working temperature of the electroplating solution is 50-60 ℃; The method comprises the steps of adopting a graphite plate as an anode and adopting a double-anode system, controlling the current density of a cathode to be in the range of 1-5A/dm < 2 > through a direct current power supply in the electroplating process, and obtaining a metal cobalt layer on the surface of a substrate under the process condition, wherein the electroplating duration is 1-8 minutes; S3, intermediate cleaning and activation: Taking out the substrate plated with the cobalt layer from the cobalt electroplating solution, fully flushing the substrate with flowing deionized water, immersing the substrate into an H 2 SO 4 solution formed by mixing 98% concentrated sulfuric acid and deionized water according to a volume ratio of 5:100, immersing for 10-30 seconds, flushing the substrate with deionized water again, and rapidly transferring the substrate into a manganese electroplating bath; s4, electroplating a manganese functional layer: Taking a substrate which is subjected to intermediate activation treatment and has a cobalt layer on the surface as a cathode, and suspending in a manganese electroplating solution, wherein the manganese electroplating solution is a sulfate system, and the sulfate system comprises 100-150 g/L of manganese sulfate (MnSO 4 ·H 2 O), 100-200 g/L of ammonium sulfate ((NH 4 ) 2 SO 4 ), 0.15-0.3g/L of selenium dioxide (SeO 2 ) and 7.2-7.5g/L of saccharin (C 7 H 5 NO 3 S); The pH of the electroplating solution is maintained to be 5.0-7.0 by using dilute sulfuric acid, the working temperature of the electroplating solution is controlled to be lower than 25-35 ℃, and a high-purity metal manganese plate is used as a soluble anode; In the electroplating process, controlling the cathode current density to be in the range of 1-6A/dm < 2 > through a direct current power supply, setting the electroplating duration to be 3-10 minutes according to the thickness of the required manganese layer, and obtaining a metal manganese layer on the surface of the cobalt layer under the process condition; s5, in-situ preparation of a coating: and placing the prepared coating sample into a sintering furnace for carrying out the progressive heat treatment. Raising the temperature from room temperature to 900-1000 ℃ at the temperature raising rate of 3 ℃ per minute, preserving the heat for 5-20 h hours at the corresponding temperature, eliminating the internal stress generated in the electroplating process, promoting the mutual diffusion between the cobalt layer and the manganese layer, and finally converting the cobalt layer and the manganese layer into a continuous and compact oxide Mn-Co coating through solid-state reaction sintering; s6, high-temperature oxidation: And (3) carrying out constant-temperature oxidation treatment on the substrate with the Mn-Co coating formed on the surface at 750-850 ℃ under the air condition, wherein the treatment time is 20-168 hours, and testing the specific surface resistance of the oxidized coated sample.
  2. 2. The method according to claim 1, wherein the ferrite stainless steel selected in the step S1 is one of SUS430, SUS441, crofer 22APU, AMG232, the sample is cut into 12mm wafers, and the samples are polished by progressively selecting 400#, 600#, 800#, 1200#, 1500# to 2000# SiC sandpaper.
  3. 3. The method according to claim 1, wherein the metallic cobalt layer in step S2 has a thickness of 1-8 μm.
  4. 4. The method according to claim 1, wherein the thickness of the metal manganese layer in step S4 is 4-5 μm.
  5. 5. SOEC metal connector Mn-Co coating obtainable by the process according to any of claims 1 to 4.
  6. 6. Use of the SOEC metal connector Mn-Co coating of claim 5 in metal connectors.

Description

SOEC metal connector Mn-Co coating and preparation method and application thereof Technical Field The invention relates to an Mn-Co coating of an SOEC metal connector, a preparation method and application thereof, belonging to the technical field of solid oxide electrolytic cells. Background Solid oxide cells (SOECs) are a highly efficient, environmentally friendly all-solid-state electrochemical device that can produce green hydrogen or green synthesis gas by electrolysis of water. The connector is a key component in the SOEC stack and plays roles of connecting single cells, separating oxidant and fuel gas and conducting current. In order to meet the requirements of working environments (high temperature, oxidation and reduction atmospheres), ferritic stainless steel is the preferred material for metal connectors because of its coefficient of thermal expansion matching with the battery assembly, low cost and ease of processing. However, ferritic stainless steel faces two major challenges in the high temperature (600-800 ℃) environment of SOEC long-term operation, namely 1) that an oxide layer (mainly Cr 2O3) is formed on the surface, which leads to a sharp increase in contact resistance and a decrease in battery performance, and 2) that Cr 2O3 reacts with water oxygen to generate gaseous CrO 2(OH) 2, migrates to the cathode and deposits, which leads to cathode "chromium poisoning" and severely decreases the electrochemical performance of the battery. To solve the above problems, it is currently the most effective means to apply a protective coating to the surface of a metal connector. Among them, mn-Co spinel coatings are widely studied for their excellent high temperature conductivity, coefficient of thermal expansion matching the substrate, and good chromium resistance. The existing coating preparation methods such as Physical Vapor Deposition (PVD), plasma spraying, screen printing method and the like have the defects that equipment of PVD and plasma spraying technology is expensive, the process is complex, workpieces with complex shapes are difficult to prepare by the screen printing method, and the compactness of the coating is poor, so that the large-scale industrial application of the coating is limited. As a mature liquid phase deposition technology, the electroplating method has the outstanding advantages of low cost, simple equipment, high deposition rate, capability of obtaining uniform coating on a substrate with a complex shape, and the like. However, the MnCo alloy coating prepared by the one-step method is difficult due to the difference of electrode potentials of Mn and Co, and the binding force between the coating and a substrate and the compactness of the coating still need to be optimized. Disclosure of Invention The invention aims to overcome the defects and the shortcomings of the prior art and provide a preparation method for preparing an Mn-Co spinel coating of an SOEC metal connector in situ based on an electroplating method. The process constructs an Mn-Co coating with gradient change of components, structures and functions from inside to outside on the surface of a metal connector by adopting an in-situ preparation process combining step electroplating and subsequent heat treatment. The coating can form stronger combination with the matrix, can effectively inhibit oxygen ion internal diffusion and chromium element outward volatilization, and finally obviously reduces the surface specific resistance of the connector. Another object of the present invention is to provide a high performance, low cost, long life SOEC metal connector mn—co coating prepared by the above process. Technical proposal A method for preparing an SOEC metal connector Mn-Co coating in situ, comprising the following steps: s1, substrate pretreatment: Selecting ferrite stainless steel as a metal connector matrix material (sample), and sequentially mechanically polishing and polishing the sample, wherein preferably, 400# SiC sand paper, 600# SiC sand paper, 800# SiC sand paper, 1200# SiC sand paper and 1500# SiC sand paper are selected step by step to polish and polish the sample; Placing the treated sample in an alkaline solution or an acetone solution for ultrasonic cleaning for 10-20 minutes to thoroughly remove oil stains and impurities on the surface, wherein the alkaline solution is preferably an aqueous solution containing 50-80 g/L sodium hydroxide (NaOH), and the operation temperature is maintained at 30-50 ℃; and then sequentially carrying out ultrasonic cleaning for 5-10 minutes by using deionized water and absolute ethyl alcohol for a plurality of times, ensuring that the residual alkali liquor on the surface is thoroughly removed, and then placing the solution in a drying environment for standby to prevent secondary oxidation. Finally, immersing and activating the sample in an acid solution for 1-3 minutes to remove an oxide film with extremely thin surface and activate the surface, wherein the acid s