Oxygen reduction activity of sulfur-functionalized Ti3C2S2 supported single-atom catalysts by first-principles calculations

Developing the oxygen reduction reaction (ORR) catalysts with high catalytic activity and low cost is necessary to improve the energy conversion efficiency of hydrogen fuel cells. MXenes with oxygen-functional terminals have been extensively used as the substrate materials of single-atom electrocatalytsts. Herein, the novel sulfur-functionalized Ti3C2S2 supporting 3d, 4d, and 5d transition metal (TM) atoms (TM = Fe, Co, Ni, Cu, Ag, Au, Ir, Os, Pd, Pt, Rh, and Ru) are theoretically constructed and investigated for their ORR activity and stability by the first-principles calculations. Ni/Ti3C2S2, Pd/Ti3C2S2, and Ir/Ti3C2S2 are screened as the potential ORR catalysts based on their lower overpotentials, while the single-atom Fe, Ru, and Os with unfilled d electrons and Cu, Ag, and Pt with filled d electrons exhibit high overpotentials up to about 1 V. Compared with Ti3C2O2, Ti3C2S2-based single-atom catalysts show higher ORR activity due to the larger charge density and moderate adsorption ability to oxygen intermediates.