Method of Direct Electrochemical Oxidation For Modifying Carbon Felts of Flow Battery

Patent metadata

Field	Value
Publication number	US-2016359186-A1
Application number	US-201514732873-A
Country	US
Kind code	A1
Filing date	Jun 8, 2015
Priority date	Jun 8, 2015
Publication date	Dec 8, 2016
Grant date	—

Abstract

A method of direct electrochemical oxidation is provided to modify carbon felts of a flow battery. Redox reactions are used for modification. Therein, voltage is directly conducted to the cell stack. The carbon felts of the cell stack are uniformly contacted with electrolytes for processing electrochemical reactions. As a result, modification is done to generate oxygen-containing functional groups (—COOH, —OH) on surfaces of the carbon felts. Thus, the present invention has the following advantages: Operation and procedure are easy and quick. Experimental parameters and conditions can be easily regulated and replaced without dismantling a device used for modification. The device used can withstand a wide range of voltage and current. Modification effect can be obtained with low cost yet without high-temperature treatments.

First claim

What is claimed is:

1 . A method of direct electrochemical oxidation for modifying carbon felts of a flow battery, comprising steps of:
(a) assembling a cell stack with electrodes made of unmodified carbon felts; (b) entering prepared electrolytes into said cell stack through pumps from an anode inlet and a cathode inlet of said cell stack to be uniformly contacted with said carbon felts under a flow rate between 20 to 100 milli-liters per minute (mL/min); flowing out said electrolytes from an anode outlet and a cathode outlet to be collected in electrolyte reservoirs; recycling said electrolytes to said anode inlet and said cathode inlet to be pumped into said cell stack until air in said cell stack is completely exhausted; (c) connecting said electrodes, which comprises an anode electrode and a cathode electrode, with an external power supply to conduct voltage under a constant voltage mode to process electrochemical redox reactions; (d) after finishing conducting voltage, entering air into said cell stack through said anode inlet and said cathode inlet of said cell stack by using said pumps under a flow rate between 20 to 100 mL/min; exhausting air through said anode outlet and said cathode outlet; completely expelling said electrolytes originally held in said cell stack to said electrolyte reservoirs; (e) replacing said electrolytes with an aqueous solution of 1 M to 3 M of vanadyl sulfate and an aqueous solution of 1 M to 5 M of an inorganic acid to be entered into said cell stack through said anode inlet and said cathode inlet of said cell stack to be uniformly contacted with said carbon felts under a flow rate between 20 to 100 mL/min; after flowing out said electrolytes through said anode outlet and said cathode outlet to be collected to said electrolyte reservoirs, recycling said electrolytes to said anode inlet and said cathode inlet of said cell stack to be pumped into said cell stack until air in said cell stack is completely exhausted; and (f) connecting said anode electrode and said cathode electrode with said external power supply to conduct a current between 40 milli-amperes per square centimeter (mA/cm 2 ) and 80 mA/cm 2 under a constant current mode to process charge and discharge reactions in said cell stack of a flow battery; and repeating said charge and discharge reactions until said cell stack is completely charged.

2 . The method according to claim 1 ,
wherein, in step (a), said cell stack comprises a separation film; two gaskets, said gaskets sandwiching said separation film; two electrodes, said electrodes sandwiching said two gaskets, said electrodes being an anode electrode and a cathode electrode, said electrodes being made of unmodified carbon felts; two flow limiting plates, said flow limiting plates sandwiching said electrodes, one of said flow limiting plates having an anode inlet and a cathode inlet, the other one of said flow limiting plates having an anode outlet and a cathode outlet; and two end plates, said end plates sandwiching said flow limiting plates.

3 . The method according to claim 1 ,
wherein, in step (b), said electrolytes are selected from a group consist of 0.1 mole (M) to 5 M of sulfuric acid, 0.1 M to 5 M of hydrochloric acid, 0.1 M to 5 M of nitric acid and 0.1 M to 5 M of phosphoric acid.

4 . The method according to claim 1 ,
wherein, in step (c), said voltage conducted is a voltage between 1.5 volts per cell (V/cell) and 2.5V/cell.

5 . The method according to claim 1 ,
wherein, in step (c), said voltage is conducted for 5 to 20 minutes.

6 . The method according to claim 1 ,
wherein, in step (c), said voltage is conducted at an operating temperature between 20 Celsius degrees (° C.) and 30° C.

7 . The method according to claim 1 ,
wherein, in step (e), said inorganic acid is selected from a group consist of sulfuric acid, hydrochloric acid, nitric acid and phosphoric acid.

8 . The method according to claim 1 ,
wherein said cell stack is obtained by assembling a plurality of single cells.

Assignees

• Inst Nuclear Energy Res Atomic Energy Council Executive Yuan Roc

Inventors

• Hsu Ning-Yih
• Chou Yi-Sin
• Chiang Heng-Wei
• Chang Yuan-Ming
• Chen Kuan-Hsiang
• Chen Yu-Chun
• Wei Hwa-Jou

Classifications

• H01M8/188 Primary

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• H01M8/20

  Indirect fuel cells, e.g. fuel cells with redox couple being irreversible (H01M8/18 takes precedence) · CPC title

• Y02E60/50

  Fuel cells · CPC title