Pt nanocatalysts with uniform clump-like crystal aggregations and high electrocatalytic activities have been successfully pulse electrodeposited on the carbon electrode with a shape-control agent poly(vinyl pyrrolidone) (PVP-60000). It is shown that PVP-60000 plays a critical role in controlling the morphology and microstructure of Pt nanocatalysts. For Pt nanocatalysts deposited by introducing PVP-60000, their electrocatalytic activities towards methanol oxidation and oxygen reduction are remarkably improved due to the increased active surface area. For understanding the formation mechanism of Pt nanocatalysts, the nucleation and growth process of Pt nanocatalysts has been preliminarily studied by quantitative analysis of current versus time transient response. (C) 2012 Elsevier Ltd. All rights reserved.