Engineering Co vacancy at tetrahedral site in spinel Co3O4 to enhance the oxygen evolution reaction performance in alkaline and neutral electrolyte

Abstract

Spinel Co3O4 which possesses two types of Co sites such as Co2+ at tetrahedral site and Co3+ at octahedral site, has been regarded as a promising non-noble metal oxygen evolution reaction (OER) catalyst to replace the state-of-the-art IrO2 catalyst. Constructing cationic vacancy is an effective method to regulate the electronic structure and optimize the catalytic performance of the active site. Therefore, the spinel Co3O4 with Co vacancy at tetrahedral site (d-Zn0.3-Co3O4) or at octahedral site (d-Al0.3-Co3O4) were fabricated in this paper by alkali etching the corresponding Zn doped Co3O4 or Al doped Co3O4. Density of state (DFT) calculations show that the Co vacancy can enhance the d band center close to Fermi level. While Co vacancy at tetrahedral site can greatly enhance the catalytic activity of neighbour Co2+ site, which is even better than the traditional octahedral Co3+ site. Therefore, d-Zn0.3-Co3O4 shows the superior OER activity gives a small 293 mV (1 M KOH) and 364 mV (1 M PBS) overpotential at 10 mA cm−2 and admirable long-term stability.