▎ 摘　　要

NOVELTY - Forming a metal nanoparticle-graphene composite, comprises mixing a metal precursor with graphite oxide in the presence of a liquid medium to form a metal precursor-graphite oxide mixture, and exfoliating the graphite oxide and reducing the metal precursor in the metal precursor-graphite oxide mixture to deposit metal nanoparticles on a first major surface of a graphene sheet formed by exfoliation of graphite oxide. USE - The method is useful of forming a metal nanoparticle, preferably platinum nanoparticle-graphene composite, which is useful as electrocatalyst for forming an electrode of a proton exchange membrane fuel cell (PEMFC) (all claimed) that is useful in automotive and mobile applications and power back-up systems. ADVANTAGE - The method: provides the single-step reduction process for synthesis of the platinum-graphene electrocatalyst with enhanced performance thus improving the energy conversion efficiency of the fuel cell; and is capable of simply, economically, rapidly and efficiently forming the metal nanoparticle-graphene composite with high stability and durability and reduced energy consumption. The PEMFC exhibits the power density of at least 673 mW.cm-2, low emissions and low operating temperatures. DETAILED DESCRIPTION - Forming a metal nanoparticle-graphene composite, comprises: either mixing a metal precursor with graphite oxide in the presence of a liquid medium to form a metal precursor-graphite oxide mixture, and exfoliating the graphite oxide and reducing the metal precursor in the metal precursor-graphite oxide mixture to deposit metal nanoparticles on a first major surface of a graphene sheet formed by exfoliation of graphite oxide; or exfoliating graphite oxide in presence of hydrogen gas to form a hydrogen-exfoliated graphene sheet, and concurrently reducing a metal precursor using the hydrogen gas to disperse metal nanoparticles on a first major surface of the hydrogen-exfoliated graphene sheet. An INDEPENDENT CLAIM is included for an electrocatalyst comprising an exfoliated graphene sheet, and platinum nanoparticles dispersed on a first major surface of the exfoliated graphene sheet, where an electrochemical surface area of the electrocatalyst is at least 101.3 m2/g.