Enhancement of Pt and Pt-alloy fuel cell catalyst activity and durability via nitrogen-modified carbon supports

Abstract

Insufficient catalytic activity and durability are key barriers to the commercial deployment of low temperature polymer electrolyte membrane (PEM) and direct-methanol fuel cells (DMFCs). Recent observations suggest that carbon-based catalyst support materials can be systematically doped with nitrogen to create strong, beneficial catalyst-support interactions which substantially enhance catalyst activity and stability. Data suggest that nitrogen functional groups introduced into a carbon support appear to influence at least three aspects of the catalyst/support system: 1) modified nucleation and growth kinetics during catalyst nanoparticle deposition, which results in smaller catalyst particle size and increased catalyst particle dispersion, 2) increased support/catalyst chemical binding (or ''tethering''), which results in enhanced durability, and 3) catalyst nanoparticle electronic structure modification, which enhances intrinsic catalytic activity. This review highlights recent studies that provide broad-based evidence for these nitrogen-modification effects as well as insights into the underlying fundamental mechanisms.

Graphitic C3N4-Pt nanohybrids supported on a graphene network for highly efficient methanol oxidation

“…3a). This might arise from the presence of a large number of nitrogen atoms surrounding activated carbon atoms in the 3GN architectures, which can substantially strengthen the interaction between the metal and the support [18,19].…”

“…This would activate a large number of neighboring carbon atoms and accelerate the formation of -OH by water dissociation, and thus promote oxidative removal of the adsorbed intermediate poisoning species [19,33]. The long-term stability of gC 3 N 4 -Pt nanohybrids, Pt nanoparticles on 3GN, and 20% Pt/C electrodes for methanol electrooxidation was investigated by chronoamperometric experiments at a given potential of 0.3 V in 0.5 M H 2 SO 4 + 0.5 M CH 3 OH solution (Fig.…”

Preparation of electrocatalysts by reduction of precursors with sodium citrate

“…In our case, a colloidal Pt solution was dropped onto a carbon coated TEM grid. The colloidal solution is likely to contain Pt of higher valences in the form of PtCl [2][3][4][5][6] or in citrate complexes. Guo et al 13 and Henglein 17 have observed Pt of higher valence state when using the citrate stabilized synthesis methods.…”

Selenium functionalized carbon for high dispersion of platinum–ruthenium nanoparticles and its effect on the electrocatalytic oxidation of methanol

“…Heteroatom functional groups introduced into carbon support appear to influence not only the active sites of the carbon support, which results in smaller catalyst particle size and increased catalyst particle dispersion, but also increases support/catalyst chemical binding (or "tethering"), which in turn results in enhanced stability of the catalysts. Furthermore, the metallic NPs electronic structure is modified, which enhances intrinsic catalytic activity [14]. In spite of these advantages, developing new heteroatom functionalities for modification of the carbon materials that provide well-dispersed noble metal NPs are still desirable.…”