Chiral topological semimetal PdGa with giant spin-split Fermi-arc for oxygen reduction reaction

Oxygen reduction reaction (ORR) hold the vital role for the clean energy technologies, such as fuel cells and metal-air batteries. It starts with paramagnetic oxygen molecular in a triplet ground state and generates with diamagnetic intermediates that are all in singlet states. Both electron transfer and orbital interactions between the catalyst and the intermediate show spin-dependent character, making the reaction kinetics and thermodynamics sensitive to the spin configurations. Hence, we synthesized high-quality topological single crystals of PdGa that naturally hosts the chiral geometry. The intrinsic chiral structure associated with and long Fermi arc facilitate the electron transfer in ORR. Moreover, the topologically protected surface states originating from the d orbitals of the surface Pd atoms could weaken the oxygen intermediate adsorption strength, thus intrinsically boosting the ORR kinetics. Our work provides a new approach to design highly efficient oxygen catalysts by introducing the topological chiral order in the materials.