Self-assembled Proton Exchange Membrane Fuel Cell Catalysts And Their Performance

Fuel cells are considered as the most promising energy conversion devices in the 21^stt century for broad applications such as portable electronics and transportation,especially the direct methanol fuel cells and direct formic acid fuel cells due to their high energy density,low operation temperature,low pollution emission,easy storage and transportation of fuels,and high conversion efficiency.So far,the platinum group metals are still the main component of the fuel cell anode catalyst,but they are scarce and expensive.Although the platinum group metal catalysts have excellent catalytic activity,they are easily poisoned by surface-adsorbed intermediates,resulting in poor catalytic stability.These two factors are the main challenges for the commercialization of fuel cells.This article aims to improve the catalytic performance of Pt-group catalysts and their utilization by developing new synthesis methods,suitable catalyst supports,and unique catalyst compositions.The main research progress is as follows:?1?The surface of the pristine graphene was non-covalent functionalized by phosphomolybdic acid?HPMo?.we have realized in-situ growth of small,uniform,high-density,and well-dispersed Pd nanoflowers on pristine graphene via pH-controlled HPMo-mediated self-assembly,in which HPMo serves simultaneously as a linker,stabilizer,and structure-directing agent,and pH modulates the reduction rate to promote the kinetically controlled anisotropic overgrowth of Pd.The obtained HPMo-G supported Pd nanoflowers show a greatly enhanced electrocatalytic activity and durability compared to HPMo-G supported Pd nanospheres,graphene supported Pd nanoparticles and commercial Pd/C toward FAOR in direct formic acid fuel cells.It can be seen that the forward peak current density for the FAOR on Pd NF/HPMo-G is 1.02 A·mg^-1,which is 4.43 and 7.85 times that on Pd NS/HPMo-G and Pd NP/G,respectively.At the same time,the CO tolerance of Pd NF/HPMo-G is even higher than that of commercial E-TEK?Pt/C?.This dramatic enhanced catalytic performance can be attributed to the great synergistic effects arising from the unique nanoflower shape,the addition of HPMo,and excellent properties of pristine graphene.?2?We present a novel and convenient approach for the synthesis of G@N-rich C@Pt NPs hybrids with the assistance of the GIL.The G@N-rich C was synthesized via direct hydrothermal growth of GIL on pristine graphene.The obtained G@N-rich C@Pt catalyst exhibites 4.19 and 5.66 times higher catalytic current densities than G@Pt and commercial Pt/C catalysts,respectively.It also shows superior durability toward methanol oxidation reaction.The high performance of G@N-rich C@Pt is mainly attributed to the great synergistic effect of the addition of N-rich C,Pt nanoparticles and pristine graphene.The synergistic effect can promote the electrochemical oxidation process.This work provides an easy way to prepare low-Pt loading but high-performance anode catalysts for direct methanol fuel cells.