Direct Control of Electron Spin at Chiral Active Sites for Highly Efficient Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) in acidic suffers from sluggish kinetics owing to the spin-dependent electron transfer process. However, the direct generation of spin-polarized electron at catalytic active sites remains elusive and the underlying mechanism is still controversial due to the lack of intrinsically homochiral catalysts. To address this challenge, we demonstrate the topological homochiral PdGa (TH PdGa) crystal with chiral active sites for ORR. Spin-resolved photoemission and theoretical simulations probed the in-situ generated spin polarizations at Pd sites. Both structural chirality and spin-orbital coupling are essential for inducing spin polarization. TH PdGa with remarkable concentration of spin-polarized electron outperforms the benchmark Pt/C by about 70 times in terms of kinetic current density at 0.85 V vs. the reversible hydrogen electrode (RHE) and over 200 times in terms of the turnover frequency. This work allows us to elucidate the respective contributions of spin polarization to the enhanced acidic ORR activity.