RuCore—Ptshell nanocatalysts with 1˜3 atomic layers of Pt-shell were developed for enhancing the catalytic activities. Uniform atomic layers of Pt were successfully deposited on the core nanoparticles with high precision. Using such nanocatalysts as the cathode of the dye-sensitized solar cell (DSSC), the efficiency of DSSC can be significantly increased. For direct methanol fuel cell (DMFC) applications, much higher performance can also be achieved by using such RuCore—Ptshell nanocatalysts and the DMFC can be operated at room temperature without the need to raise the cell temperature to above room temperature (such as 80° C.).