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 similar to 256 mV to achieve the current density of 10 mA cm(-2), Tafel slope drops as low as similar to 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.

Automated summary

This study demonstrates that by introducing oxygen vacancies into the inert oxidation layer on metallic cobalt sulfide, and by incorporating zinc into the structure, significant improvements in electrocatalytic activity can be achieved. This fabricated Zn doped CoOx/Co9S8 nanotube arrays exhibit remarkable electrocatalytic activity with a low overpotential and good long term stability.