Synthesis of Ordered Pt Nanocube Arrays Directed by Block Copolymer Nanotemplate and Their Potential on Ethanol Oxidation Reaction

Pt38 as a promising ethanol catalyst: a first principles study

This first-principles study predicts Pt₃₈ nanoparticles as a catalyst for ethanol reactions. Starting from the adsorption properties, we shed light on the effectiveness of Pt-based nanoclusters as ethanol catalysts. First, the ethanol adsorption on Pt₃₈ shows that the most stable site positions the molecule with the oxygen anchored on top of an edge, whereas CH₃ is oriented towards the facet and the molecule remains in trans-symmetry. The ethanol-oxygen adsorbed on top of a facet Pt-atom offers the least stable configuration and the longer Pt-O distance (2.318 Å), while the shorter Pt-O distance (2.237 Å) is found when ethanol is on top of an edge site and the molecule is vertically oriented with Gauche symmetry. A shorter Pt-O distance correlates with higher radial breathing of the nanoparticle after ethanol adsorption. Atomic charge redistribution is calculated on all the considered systems and cases. In any event, we show that the Pt-anchor receives a charge, whilst oxygen-ethanol donates electrons. Orbital analysis shows that Pt-anchors and ethanol-oxygen atoms primarily exchange p-charge. Energy barriers associated with the ethanol bond cleavage show that the C-C bond break is slightly more favourable on Pt₃₈ than on an extended Pt(111). In addition, we find that the cleavage of the hydroxyl O-H ethanol bond shows a higher energy barrier while the removal of an H-atom from the CH₃ group is easier. These three facts indicate that the Pt₃₈ nanoparticle enhances ethanol catalysis and hence is a good candidate for ethanol-based fuel cells.

Highly Ordered Pt-Based Nanoparticles Directed by the Self-Assembly of Block Copolymers for the Oxygen Reduction Reaction

Designing Pt-based nanoparticle (NP) catalysts is of great interest for the lowering of Pt usage and the enhancement of catalytic activity on the proton-exchange membrane fuel cells (PEMFCs). However, it is still challenging to develop well-arrayed catalyst NPs on supports over multiple-length scales. Herein, we presented a facile strategy of producing well-ordered Pt-based NPs toward oxygen reduction reaction (ORR) catalysts assisted by the self-assembly of block copolymers. In contrast to the conventional Pt/C ORR catalysts with a random dispersion on carbon, the as-prepared Pt, PtCo, and PtCo@Pt NPs in our work were hexagonally arranged with a uniform quasi-spherical shape and ordered distribution. The systematic study related to their ORR activities revealed that the PtCo@Pt core-shell NP arrays were more active and more durable than PtCo, Pt, and the commercial Pt/C catalyst. In the rotating-disk electrode test, a half-wave potential (E_1/2) of 0.86 V versus RHE and a 4-e ORR mechanism were found for PtCo@Pt. Single-cell performance showed that the current density and the peak power density of PtCo@Pt achieved 0.86 A/cm²@0.7 V and 1.05 W/cm², respectively, with a Pt loading of ∼0.15 mg/cm² on the cathode. Also, they held 81.4 and 82.9% retention, respectively, after the durability test in the single-cell test. Density functional theory calculation results revealed that PtCo@Pt NPs had a lower d-band center and a weaker oxygen binding energy compared to Pt and PtCo, which contributed to the enhancement of the ORR activity.