Multi-scale regulation in S, N co-incorporated carbon encapsulated Fe-doped Co9S8 achieving efficient water oxidation with low overpotential

Abstract

Sulfide compounds provide a type of promising alternative for oxygen evolution reaction (OER) electrocatalysts due to their diversity, intrinsic activities, low-price and earth-abundance. However, the unsmooth mass transport channel, the collapse of the structure and insufficient intrinsic activities limits their potential for OER performance. In respond, the dense Fe-doped Co9S8 nanoparticles encapsulated by S, N co-incorporated carbon nanosheets (Fe-Co9S8@SNC) was proposed and synthesized via fast thermal treatment from ultrathin metal-organic frameworks (MOFs) nanosheets. In designed catalysts, the nanosheet configuration connected by nanoparticles retained rich access for permeation of electrolyte and precipitation of O2 bubbles during OER process. Meanwhile, the outer carbon layer of Co9S8 provided additional catalytic activity while acting as armor to keep the structure stability. At the atomic scale, the doped Fe regulated the local charge density and the d-band center for facilitating desorption of oxygen intermediates. Benefiting from this multi-scale regulation strategy, the Fe-Co9S8@SNC displays an ultralow overpotential of 273 mV at 10 mA·cm−2 and small Tafel slope of 55.8 mV·dec−1, which is even close to the benchmark RuO2 catalyst. This concept could provide valuable insights into the design of other catalysts for OER and beyond.