Platinum nanoparticle catalysts for electrochemical hydrogen pumping were synthesized on a functionalized powder carbon substrate (XC72R) using atomic layer deposition (ALD) in a fluidized bed reactor (FBR). Trimethyl(methylcyclopentadienyl)platinum(IV) (MeCpPtMe3) was used as the reagent for platinum delivery. Following deposition, MeCpPtMe3 ligands were combusted or hydrogenated to yield platinum on the XC72R surface. Reactions throughout the ALD cycle were monitored using mass spectrometry and IR spectroscopy to clarify the deposition chemistry. The resultant platinum catalysts were compared to commercial products in hydrogen pumping tests. Hydrogenation made finer, more dispersed, platinum nanoparticles that performed similarly to their commercial equivalent when pumping hydrogen. Conversely, oxygenation made a coarser catalyst that underperformed its commercial equivalent. Thus, altering chemistries shows potential for improving ALD catalyst performance. (C) 2015 Elsevier B.V. All rights reserved.