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

Spinel Co 3 O 4 which possesses two types of Co sites such as Co 2+ at tetrahedral site and Co 3+ at octahedral site, has been regarded as a promising non-noble metal oxygen evolution reaction (OER) catalyst to replace the state-of-the-art IrO 2 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 Co 3 O 4 with Co vacancy at tetrahedral site (d-Zn 0.3 -Co 3 O 4 ) or at octahedral site (d-Al 0.3 -Co 3 O 4 ) were fabricated in this paper by alkali etching the corresponding Zn doped Co 3 O 4 or Al doped Co 3 O 4 . 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 Co 2+ site, which is even better than the traditional octahedral Co 3+ site. Therefore, d-Zn 0.3 -Co 3 O 4 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.