Pt nanoparticles supported on nitrogen-doped porous carbon microspheres (Pt/C-N) were synthesized via an in-situ spray-drying technique followed by calcination. The addition of ammonium hydroxide had a remarkable influence on the solution chemistry, which promoted the simultaneous formation of metallic Pt and nitrogen doping onto carbon support material. Furthermore, the precursor pH influenced the subsequent oxygen reduction activity of the product. Ultrahigh oxygen reduction reaction (ORR) activity was recorded for a catalyst prepared at a precursor pH of 8.4 with mass activity and specific activity were 564 mA mg(-1) Pt and 834 mu A cm(-2) Pt, respectively. This investigation resulted in an effective strategy to escalate the catalyst ORR during limited catalyst surface area enhancement (C) 2012 Elsevier B.V. All rights reserved.