Diminutive tuning of lattice oxygen controlled by sulfur-mediated vacancies for oxygen evolution reaction

Though heteroatom-doped metal-based electrocatalysts are estimated to display potential advantages in oxygen evolution reaction (OER), the great distortion of their bulk lattice by corresponding heteroatoms usually lead to irreversible structure deformation and thus unacceptable durability. In this work, we propose a novel "minimally invasive surgery" (MIS) design to delicately modify the electrocatalyst lattice to match the requirement of both high efficiency and long lifespan for OER. Briefly, NiFe-layered double hydroxide (LDH) is accurately doped with only 2.98 at. % sulfur which influences crystal oxygen, showing great enhancement on both kinetics and stability. Careful characterizations disclose that the main skeleton of NiFe-LDH is highly retained while the sulfur doping induces specific vacancies of lattice oxygen (O_Vs), which confirms structural integrity as well as reasonably activated electrocatalytic sites. As a result, this unique electrocatalyst (NiFe-Ni@S) displays boosted performance of OER, showing superior performance and durability to commercial noble-metal-based electrocatalysts. Density functional theory (DFT) calculations indicate that the introduction of sulfur can mediate the optimization of vacancies and rationally tune the adsorption energy of O₂-containing intermediates. This work provides insights into the key role of doping states and degree of congeners, aiming at realizing electrocatalyst reversibility while achieving enhanced electrocatalysis efficiency.