We have developed a method for fabrication of Au nanoparticle platelets which can be coated onto the Nafion membranes of polymer electrolyte membrane (PEM) fuel cells simply by Langmuir-Blodgett (LB) trough lift off from the air water interface. Incorporating the coated membranes into fuel cells with one membrane electrode assembly (MEA) enhanced the maximum power output by more than 50% when operated under ambient conditions. An enhancement of more than 200% was observed when 0.1% CO was incorporated into the H-2 input gas stream and minimal enhancement was observed when the PEM fuel cell was operated with 100% O-2 gas at the cathode, or when particles were deposited on the electrodes. Density function theory (DFT) calculations were carried out to understand the origin of improved output power. Au NPs with 3-atomic layer in height and 2 nm in size were constructed to model the experimentally synthesized Au NPs. The results indicated that the Au NPs interacted synergistically with the SO3 groups, attached at end of Nafion side chains, to reduce the energy barrier for the oxidation of CO occurring at the perimeter of the Au NPs, from 1.292 eV to 0.518 eV, enabling the reaction to occur at T < 300 K. (C) 2016 Published by Elsevier inc.