d-Band center modulating of CoOx/Co9S8 by oxygen vacancies for fast-kinetics pathway of water oxidation

Metallic cobalt-based sulfide, selenide and phosphide will undergo superficial transformation into insufficient activity cobalt oxides/(oxy)hydroxides during the oxygen evolution reaction (OER) process, which limits the efficiencies of electrical-conversion applications. It is necessary to activate the inert oxidation layer on the surface of metallic compounds for highly efficient OER catalysts. Taking cobalt sulfide as an example, we designed a facile strategy to introduce oxygen vacancy (Vo) in the inert oxidation layer CoOx coating on metallic Co9S8 by in-situ derived Zn doped Co9S8. First-principles calculation and experimental analysis verify that introduced Vo leads to lesser electron filling of the anti-bonding states by tailoring the positions of d-band center, which can facilitate the fast kinetics of OER. Meanwhile, internal metallic Zn-Co9S8 can accelerate the electron transfer process. Benefiting from the advantages of geometric construction and electronic regulation, fabricated Zn doped CoOx/Co9S8 nanotube arrays exhibit remarkable electrocatalytic activity with a low overpotential of ~ 256 mV to achieve the current density of 10 mA cm−2, Tafel slope drops as low as ~ 44 mV dec−1, accompanied by good long term stability toward OER conditions. The present work provides valuable insights into the design of other catalysts for OER and beyond.