Morphological control of carbon-supported Pt-based nanoparticles via one-step synthesis

Abstract

The morphology of Pt-based nanoparticles supported on carbon is controlled to enhance the oxygen reduction reaction (ORR) catalytic performance. Herein a simple one-step method without a polymer surfactant is demonstrated to synthesize Pt-Cu nanoclusters, Pt-Cu nanospheres, and Cu-doped Pt nanoplates. Metal precursors are reduced by sodium tetrahydroborate in a NaCl or NH4Cl aqueous solution containing carbon supports, and nanoparticles are directly deposited on carbon. Cl− ions generated from NaCl or NH4Cl delay the reduction of metal ions when O2 is dissolved in the synthesis solution, leading to larger particles. In addition, NH4+ ions guide the growth direction of Pt to form a plate-like morphology that exposes the {111} facets. However, stable amine complex lowers the Cu content in the nanoplates. Nanoclusters and nanospheres are obtained in the absence of Cl−/O2 and NH4+, respectively. Half-cell measurements are performed in acidic media to evaluate the electrochemical properties. Cu-doped Pt nanoplates exhibit a 3.67-times higher ORR catalytic activity than the commercial Pt catalysts thanks to the synergistic effect with a small amount of Cu and selective exposure of the {111} facets. The result suggests that transition metals in Pt-based electrocatalysts may be unnecessary to form intermetallic alloyed crystals for the enhanced ORR performance.