張守仁/張佳楠在Small上發表論文：軸配位Cr-N-C助力非鐵基ORR催化劑
Because of the instability and Fenton reactivity of non-precious metal nitrogen-carbon (e.g. Fe-N-C)-based catalyst when processing the oxygen reduction reaction (ORR), seeking for electrocatalysts highly efficient performance becames very highly desired to speed up the commercialization of fuel cell. Herein, chromium (Cr)-N4 electrocatalyst containing extraterrestrial S formed axial S1-Cr1N4 bonds (S1-Cr1N4-C) was achieved via a assembly polymerization and confined pyrolysis strytegy. Benifiting from the adjusting the coordination configuration and electronic structure of the metal center through axial coordination (N-containing ligands, O/OH/S, and Cl/I), S1-Cr1N4-C exhibits enhanced the intrinsic activity (E1/2 is 0.90 V vs. RHE in 0.1 M KOH) compared with that of Cr-N4-C (E1/2 is 0.87 V) and Pt/C(E1/2 is 0.83 V) catalysts. More notably, the catalyst is almost inert in catalyzing the Fenton reaction, and thus show the high stability. Both experimental and density functional theory (DFT) results further reveal that the existence of axial S atoms in S1-Cr1N4-C moiety has the better ORR activity than Cr1N4-C moieties. The axial S ligand in S1-Cr1N4-C moiety can break the electron localization around the planar Cr1N4 active center, which facilitated the rate-limiting reductive release of OH* and accelerated overall ORR process. The present work opens up a new avenue to modulate the axial ligand type of the single-atom active center to enhance intrinsic SAs performances.