nn8b03615_si

RoomTemperature Pressure Synthesis of

Layered Black PhosphorusGraphene

Composite for SodiumIon Battery Anodes

Yihang Liu,

1,#

Qingzhou Liu,

2,#

Anyi Zhang,

Jiansong Cai,

Xuan Cao,

Zhen Li,

Paul D. Asimow,

and Chongwu Zhou

1,*

Department of Electrical Engineering,

Department of Materials Science and

Engineering,

Department of Physics, University of Southern Calif

ornia, Los Angeles,

CA 90089, USA

Division of Geological and Planetary Sciences, Cali

fornia Institute of Technology,

Pasadena, CA 91125, USA

Y. Liu and Q. Liu contributed equally to this work.

* To whom correspondence should be addressed. Emai

l chongwuz@usc.edu

Graphene oxide (GO) preparation

: Graphene oxide (GO) water suspension was

purchased from Graphene Supermarket (Graphene Labor

atories Inc.), then was

further treated according to a modified Hummers met

hod to create more void space

between the GO layers through exfoliation.

and H

were mixed with a

volume ratio of 9:1, then 1% wt. GO water suspensio

n was added into the mixed acid

solution. The mixture was heated to 50°C and stirre

d for 10 hours, and then cooled

with ice and an appropriate amount of added H

. After standing for onehour, the

supernatant liquid was removed and the rest of the

mixture was diluted with water,

repeating the procedure several times. The remainin

g solid material was then washed

with water, HCl and ethanol several times, and then

filtered and dried at 60°C in air

overnight.

RP/rGO flash-heat-treatment synthesis:

RP fine powder with 99% purity (Spectrum

Chemical Mfg. Corp.) was dried at 90°C to remove mo

isture and sieved to pass

through a 30 μm mesh. The RP and GO powder precurso

rs were placed in a ceramic

boat with a RP/GO/RP threelayer structure with a c

eramic cover on the boat. The

mass ratio between RP and GO is 5:1. The boat with

chemicals was loaded into a tube

furnace under argon flow with a mixture of 5% hydro

gen (Ar/H

). The boat was first

placed in the location outside the hot zone. After

heating the furnace to 500°C, the

boat was moved into the hot zone. Once P condensati

on on the inner surface of the

quartz tube downstream of the hot zone was seen (~

1 minute), the boat was moved

back to the original position to cool down. The tem

perature of the boat was

maintained at 290°C overnight to convert potential

white P to red P. The resulted

RP/rGO composite was transferred into an Arfilled

glovebox, washed with methanol

and dried accordingly.

RP/rGO film preparation:

the film was prepared through vacuum filtration. A

small

amount of RP/rGO powder was first added to the filt

ration equipment to obtain a thin

layer of rGO network at the bottom. The RP/rGO comp

osite was mixed with ethanol,

and the mixture was added to form the main part of

the film. In order to obtain a

smooth film with excellent mechanical properties, t

he power of the vacuum pump and

the material loading rate during the filtration pro

cess were carefully adjusted. The

obtained film was pressed to increase the mechanica

l stability. The mass of the film

electrodes was around 2 mg each. Then the film was

transferred onto aluminum foil

for the pressure synthesis.

The RP/rGO film and GO powder was also analyzed by

Xray photoelectron

spectroscopy (XPS) to study the chemical bonding be

tween phosphorus and rGO

sheets at the surface of the composite, as shown in

Supplementary Figure S2. In

Figure S2a, the spectrum of the pristine GO sample

can be fitted with three Gaussian–

Lorentzian peaks at 284.6, 286.3, and 287.2 eV, cor

responding to C=C/C–C, C–O,

and O–C=O bonds, respectively. The spectrum of the

RP/rGO composite shows peaks

at 284.5, 285.5 and 286.5 eV, corresponding to C=C/

C–C, C–O and C=O bonds,

respectively. Compared with the GO sample, the inte

nsity of the C–O peak of the

RP/rGO composite is markedly reduced and the O–C=O

peak vanishes, indicating

that GO was thermally reduced during the heattreat

ment in an Ar/H

atmosphere. In

Figure S2b, the O 1s highresolution spectra of the

two samples also confirm the

thermal reduction of GO, as the 531.7 eV signal cor

responding to the O=C bond of

the GO sample disappeared after the heat treatment,

and only the peak of the O–C

bond at 533.1 eV was observed for the RP/rGO compos

ite.

Figure S1. Thermogravimetric analysis (TGA) data of

flashheattreatment

synthesized RP/rGO and thermally reduced rGO with t

he same heat treatment

conditions.

Figure S2. XRD pattern of the commercial red phosph

orus.

Figure S3. Highresolution (a) C 1s and (b) O 1s XP

S spectrum of the

flashheattreatment synthesized RP/rGO composite a

nd the GO sample.

Figure S4. TEM images of postcycling BP/rGO anode.

Reference

1. Marcano, D. C.; Kosynkin, D. V.; Berlin, J. M.;

Sinitskii, A.; Sun, Z.; Slesarev, A.;

Alemany, L. B.; Lu, W.; Tour, J. M. Improved Synthe

sis of Graphene Oxide.

ACS Nano

2010

, 4806

−4814