In the synthesis of rGO/Ge/rGO, the NH4H(HGeO3)2 precursor solution was first obtained by the reaction of GeO2 and NH3*H2O aqueous solution.56 GeO2 (1 g) powder was dispersed in distilled water (50 mL) by ultrasonication for 10 min. Then concentrated NH3*H2O (68%, 10 mL) was added to the above mixture with magnetic stirring and a transparent solution A was formed. Graphite oxide (GO) was synthesized through a modified Hummer's method starting from graphite powder.57 The as-synthesized GO was dispersed in distilled water and exfoliated by ultrasonication to generate sheets. Subsequently, 10 mL of exfoliated GO solution (20 mg mL-1) was dissolved in solution A under constant stirring for 30 min to obtain a brown solution and then dried at 70 degC for 12 h. Thus the NH4H(HGeO3)2/GO composite was prepared. To obtain the rGO/Ge/rGO hybrid, the NH4H(HGeO3)2/GO was annealed under a 15% H2/85% Ar flow at 800 degC for 4 h.
GeO2
dispersed
1 g
g
distilled water
50 mL
mL
GeO2
ultrasonication
10 min
min
NH3*H2O
concentrated
68%
%
NH3*H2O
added
10 mL
mL
exfoliated GO solution
10 mL
mL
exfoliated GO solution
20 mg mL-1
mg mL-1
exfoliated GO solution
constant stirring
30 min
min
brown solution
dried
70 degC
degC
brown solution
dried
12 h
h
flow
H2
15%
%
flow
Ar
85%
%
NH4H(HGeO3)2/GO
annealed
800 degC
degC
NH4H(HGeO3)2/GO
annealed
4 h
h