Anisotropic Surface Modulation of Pt Catalysts for Highly Reversible Li-O₂ Batteries: High Index Facet as a Critical Descriptor

The surface structure of solid catalysts has been regarded as a critical descriptor for determining the catalytic activities in various applications. However, structure-dependent catalytic activities have been rarely understood for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) within Li-O₂ batteries. Here, we succeeded in the preparation of a Pt catalyst with an anisotropic structure and demonstrated its high catalytic activity in nonaqueous Li-O₂ batteries. The cathode incorporating Pt exposed with high-index {411} facets showed greatly enhanced ORR and OER performance in comparison to commercial Pt/C cathode. The anisotropic Pt catalyst improved ORR activity with a large capacity of 12 985 mAh g_carbon ^-1, high rate performance, and stable cyclic retention up to 70 cycles with the capacity limited to 1000 mAh g_carbon ^-1. Furthermore, the anisotropic Pt catalyst exhibited high round-trip efficiency of ∼87% with a low OER potential (3.1 V) at a current density of 200 mA g_carbon ^-1. Our first-principles calculations revealed that the high-index facets, which contain step edge, kink, and ledge sites, are significantly more reactive than the low-index facets in terms of surface energy and O-binding energy.