Cascaded orbital-oriented hybridization of intermetallic Pd₃Pb boosts electrocatalysis of Li- O₂ battery

Catalysts with a refined electronic structure are highly desirable for promoting the oxygen evolution reaction (OER) kinetics and reduce the charge overpotentials for lithium-oxy-gen (Li-O-2) batteries. However, bridging the orbital interactions inside the catalyst with external orbital coupling between catalysts and intermediates for reinforcing OER cata-lytic activities remains a grand challenge. Herein, we report a cascaded orbital-oriented hybridization, namely alloying hybridization in intermetallic Pd3Pb followed by intermo-lecular orbital hybridization between low-energy Pd atom and reaction intermediates, for greatly enhancing the OER electrocatalytic activity in Li -O-2 battery. The oriented orbital hybridization in two axes between Pb and Pd first lowers the d band energy level of Pd atoms in the intermetallic Pd3Pb; during the charging process, the low -lying 4d(xz/yz) and 4d(z)(2) orbital of the Pd further hybridizes with 2p* and 5s orbitals of lithium superoxide (LiO2) (key reaction intermediate), eventually leading to lower energy levels of antibonding and, thus, weakened orbital interaction toward LiO2. As a consequence, the cascaded orbital-oriented hybridization in intermetallic Pd3Pb considerably decreases the activation energy and accelerates the OER kinetics. The Pd3Pb-based Li-O-2 batteries exhibit a low OER overpotential of 0.45 V and superior cycle stability of 175 cycles at a fixed capacity of 1,000 mAh g(-1), which is among the best in the reported catalysts. The present work opens up a way for designing sophisticated Li -O-2 batteries at the orbital level.