All chemicals in this work were of analytical grade and used as received. In a typical experiment, 10 mmol sodium stannate (Na2SnO3) was dissolved in 50 ml of 1 M glucose aqueous solutions. The clear solution was obtained through ultrasonic dispersion for 1 h before being transferred to a Telflon-lined stainless steel autoclave heated at 180 C for 4 h. The precipitates were harvested by centrifugation and washed thoroughly with deionized water and ethanol several times, respectively. After drying at 80 C overnight, SnO2 powders and SnO2@C powders were obtained at 550 C for 4 h with a heating rate of 2 C/min under air and argon atmosphere, respectively. SnO2@C/Cu sample was synthesized as follows. 250 mg SnO2@C powders were dissolved in 100 ml 8 mM CuSO4 aqueous solution through ultrasonic dispersion for 1 h. Afterward, 5 ml hydrazine hydrate (N2H4.H2O) was dripped into the solution slowly. SnO2@C/Cu powders were harvested after centrifugation and dried at 80 C under vacuum.