External and Internal Interface-Controlled Trimetallic PtCuNi Nanoframes with High Defect Density for Enhanced Electrooxidation of Liquid Fuels

Selectively exposing active surfaces of Pt-based nanoframes (NFs) can promote electrocatalysis of small organic molecules, especially regarding improved diffusion and anti-poisoning properties. However, the systematic investigation on the synthesis as well as structure-property relationship of Pt-based NFs with tunable external and internal surface structures is still at its early stage. Herein, we report a facile, environmental, and one-pot approach to fabricate PtCuNi NFs with tunable external and internal surface structures by flexibly adjusting coordination and reducing agents. Interestingly, electrocatalytic results reveal that the PtCuNi NFs with variable external structures possess higher performance (activity and anti-CO-poisoning capability) than those with tunable internal structures as well as commercial Pt/C. Especially, the PtCuNi external branch nanoframes (eb-NFs) exhibit excellent specific activities of methanol and formic acid electrooxidation reactions (MOR and FAOR), 10.7 and 7.9 times higher than those of commercial Pt/C, respectively. The PtCuNi eb-NFs also possess superior diffusion ability for methanol electrooxidation (0.0276) and formic acid electrooxidation (0.0153) compared to other PtCuNi NFs with a plentiful internal surface. The enhanced MOR and FAOR activities of PtCuNi eb-NFs are ascribed to their abundant external surface area and high defect density (e.g., vacancy, subtle lattice distortion, and high-index facets), which results in an optimal anti-CO-poisoning capability as a result of the diffusion and ligand effects. This work opens up a new pathway for enhancing the electrooxidation properties (anti-poisoning property and diffusion rate) of liquid fuels by tuning the surface structures of NF catalysts.