Facile Synthesis Of Pt-based Alloy/Reduced Graphene Oxide Composites And Their Electrocatalytic Performance

The extensive applications of fuel cells provide a new generation green powersource for energy revolution. Among the fuel cells, the Proton Exchange MembraneFull cells (PEMFCs) have drawn great attention recently due to their high energydensity energy-conversion efficiency, environmental friendly, low operating temper-ature as well as the simple handling. The oxygen reduction reaction (ORR) is the keyreaction to the PEMFC performance, which is seriously dependent on cathode electr-ocatalysts.The cathode catalyst of the conventional PEMFC is the Pt/C, a catalystwith Pt nanoparticles deposited on carbon. However, the high cost of the pure Pt is anobstacle to the broad applications of PEMFCs. Moreover, pure Pt catalysts are easilypoisoned by carbon monoxide at low temperature, which is a by-product of methano,ethanol, formic acid in the electrochemical reaction. One approach that has beendemonstrated to improve the catalytic activity and stability and to lower the cost ofthe catalysts is to alloy Pt with other transition metals, such as Fe, Co, Ni, etc, anddeposite on an ideal supporting material. Recently, graphene has been considered asone of the most promising supporting materials for various catalysts due to its uniqueelectronical and mechanical properties. In the present work, a facile strategy has beendeveloped to synthesize binary alloy PtM (M=Co,Ni)/reduced graphene oxide (rG-O)and ternary alloy PtFeCo/rG-O nanocomposites. Furthermore, the eletroche-micalperformances of as-synthesized Pt-based alloy/graphene nanocomposites werestudied. The major studies in the present work include three parts as listed below:1）Graphite oxide(GO) were firstly prepared according to a modified Hummers’method; then the catalysts including binary alloy PtM (M=Co,Ni)/r-GO and terna-ry alloy PtFeCo/rG-O were synthesized via solvothermal route. The as-preparedcatalysts were characterized by HRTEM, XRD, ICP-AES, XPS and Raman. Theresults show that the GO in nanocomposites was successfully reduced into rG-Oand uniform PtNi, PtCo and PtFeCo alloy nanoparticles were homogeneouslyloaded on rG-O sheets.2）In order to explore the influence of different reaction parameters on the formationof PtM (M=Co,Ni)/r-GO and PtFeCo/rG-O nanocomposites, a series of syntheseswere carried out by adjusting the reaction parameters, such as the addition of reducing agent (1,2-hexadecane glycol), the amount of metal salts and GO, andthe addition of surfactant (Lys). The results show that the distribution density,morphology, and size of PtM (M=Co,Ni)/r-GO nanoparticles on rG-O sheets wasstrongly influenced by the addition of reducing agent.While PtFeCo nanoparticleson rG-O sheets were strongly influenced by the amount of metal salts and Lys.3) The electrocatalytic performance of as-synthesized PtM (M=Co,Ni)/rG-O andPtFeCo/rG-O nanocomposites was investigated through cyclic voltammetry (CV)and liner sweep voltammetry (LSV), and compared with that of the commercialPt/C (20wt.%). The results show that the electrochemical activity of binary alloyPtM (M=Co,Ni)/rG-O was only one-third of Pt/C (20wt.%). Moreover, the eletr-ochemical activity was in an order of PtM (M=Co,Ni)/rG-O> PtM (M=Co,Ni)/rG-O-1,2-hexadecane glycol. For ternary alloy PtFeCo/rG-O nanocomposites, theelectrochemical activity was decreased sharply in the presence of the Lys.Thestability of binary alloy PtM (M=Co,Ni)/rG-O and ternary alloy PtFeCo/rG-Onanocomposites is higher than commercial Pt/C (20wt.%).In summary, PtM (M=Co,Ni)/rG-O and PtFeCo/rG-O nanocomposites have beensuccessfully synthesized via one-pot solvothermal method. The PtCo, PtNi, andPtFeCo nanoparticles were homogenously loaded onto the network of rG-O sheets.The synthesis approach is simple and low-cost and can be used for the synthesis ofother Pt-M/rG-O nanocomposites for applications in catalysis and energy.