# US 11,897,772 B2 · Method of preparation of reduced graphene oxide(rGO)

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- Number: US 11,897,772 B2
- Document ID: US11897772B2
- Status: Granted
- Kind: B2
- Application number: 17/056,967
- Filed: 2019-05-22
- Published: 2021-08-05
- Granted: 2024-02-13
- Earliest claimed: 2018-05-23
- Assignees: Tata Steel Limited; Centre for Nano and Soft Matter Sciences
- Applicants: Tata Steel Limited; Centre for Nano and Soft Matter Sciences
- Inventors: Anand Sen; Sumitesh Das; Shyam Kumar Choudhary; Giridhar Udapi Rao Kulkarni; Murali Gedda; Rajashekhar Ningappa Pujar
- Web page: https://patentgrep.com/patent/US11897772B2

## CPC

- C01B 32/198: Graphene oxide
- C01B 32/23: Oxidation
- C01P 2006/12: Surface area
- C01P 2006/40: Electric properties
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

The present disclosure provides a simple and inexpensive method to produce reduced Graphene oxide (rGO). The method comprises conversion of low-cost carbon sources such as coal tar pitch (industrial by-product) into a high quality rGO wherein said conversion is carried out by annealing the carbon source at two different temperatures. The rGO is obtained at high yields by employing the present method and the obtained rGO demonstrates high conductivity and good surface area along with very low oxygen content.

## Claims

### Claim 1

A method of preparing reduced Graphene Oxide (rGO) comprising:
a) heating a carbon source at temperature ranging from about 480° C. to 520° C.;
b) cooling the heated carbon source; and
c) heating the cooled carbon source under vacuum at temperature ranging from about 850° C. to 950° C., to obtain the rGO.

### Claim 2 (depends on 1)

The method as claimed in claim 1, wherein the carbon source is coal tar pitch.

### Claim 3 (depends on 2)

The method as claimed in claim 2, wherein the coal tar pitch has a softening temperature of about 80° C. to 110° C., ash content of about 0 to 0.4%, quinoline insoluble (QI) of about 3% to 16%, toluene insoluble (TI) of about 16% to 22% and a moisture content of about 0 to 0.5%.

### Claim 4 (depends on 1)

The method as claimed in claim 1, wherein heating the carbon source in step a) is performed at the temperature of about 490° C. to 510° C.

### Claim 5 (depends on 1)

The method as claimed in claim 1, wherein the heating in step a) is carried out for a time-period ranging from about 60 minutes to 75 minutes.

### Claim 6 (depends on 1)

The method as claimed in claim 1, wherein the heated carbon source in step b) is cooled to a temperature range of about 20° C. to 30° C.

### Claim 7 (depends on 1)

The method as claimed in claim 1, wherein heating the cooled carbon source in step c) is performed at the temperature of about 880° C. to 900° C.

### Claim 8 (depends on 1)

The method as claimed in claim 1, wherein the heating in step c) is carried out for a time-period ranging from about 15 minutes to 30 minutes.

### Claim 9 (depends on 1)

The method as claimed in claim 1, wherein the vacuum in step c) ranges from about 1×10−1 to 1×10−2 millibar.

### Claim 10 (depends on 1)

The method as claimed in claim 1, wherein the prepared rGO has a conductivity ranging from about 1900 S/cm to 2100 S/cm.

### Claim 11 (depends on 1)

The method as claimed in claim 1, wherein the rGO has a surface area ranging from about 45 m2 g−1 to 55 m2 g−1.

### Claim 12 (depends on 1)

The method as claimed in claim 1, wherein a yield of rGO ranges from about 85% to 95% with respect to the carbon source.

### Claim 13 (depends on 1)

The method as claimed in claim 1, wherein the prepared rGO has a conductivity of 2000 S/cm.

### Claim 14 (depends on 1)

The method as claimed in claim 1, wherein the rGO has a surface area of about 50 m2 g−1.