Hollow platinum tetrapods: using a combination of {111} facets, surface concave topology, and ultrathin walls to boost their oxygen reduction reactivity

Abstract

Hollow nanocages with ultrathin walls and specific configurations have been reported to have stellar performances towards various catalytic reactions owing to their high atom utilization efficiency and well-defined facets/architectures. Herein, we for the first time report a facile synthesis of ultrathin Pt hollow tetrapods (HTPs) that consist of four nanothorn-like ultralong branches with an average wall thickness of six atomic layers. Based on seed-mediated growth on Pd tetrapods, we systematically evaluated the factors for conformal deposition of Pt skin to ensure that the {111} facets and surface concave topology of Pd tetrapods could be well-preserved after subsequent Pd etching. The resultant ultrathin Pt HTPs show a superior electro-catalytic activity and stability for the acidic oxygen reduction reaction (ORR), with E_onset of 1.014 V, E_1/2 of 0.836 V, and a specific activity of 0.804 mA cm⁻² at 0.90 V, outperforming those of the Pd@Pt_6L core–shell tetrapods and Pt/C. Specifically, (i) the ultrathin Pt hollow skin guarantees a high metal utilization; (ii) the uniform {111} facets, porosity, and inhomogeneous surface distribution of defects/steps point to a large specific activity; (iii) the self-sustentive four-angle skeleton sustains long-range electro-catalytic stability.