Highly Dispersive Cobalt Oxide Constructed in Confined Space for Oxygen Evolution Reaction

Cobalt-based catalysts are highly promising for the oxygen evolution reaction (OER) in terms of both cost and performance. The dispersion state of Co ₃ O ₄ impacts the catalyst performances directly, while development of an efficient method for Co ₃ O ₄ dispersion remains a pronounced challenge. In this study, it is the first time that the confined space strategy (CSS) is employed to make highly dispersive Co ₃ O ₄ on the mesoporous silica (MS) SBA-15. The precursor of Co ₃ O ₄ is successfully introduced into the confined space inherent in as-prepared SBA-15 (between the silica walls and the template). The CSS facilitates the formation of Co ₃ O ₄ with extremely high dispersion after the decomposition of Co precursor. Up to 4 mmol of Co ₃ O ₄ can be dispersed in per gram of MS without any X-ray diffraction lines (the obtained sample is denoted as 4CoAS), while obvious diffraction lines are detected in the counterpart prepared from calcined SBA-15 (the sample is denoted as 4CoCS). Further calculation indicates that the size of Co ₃ O ₄ nanoparticles in 4CoCS is 9.8 nm, which is much larger than that in 4CoAS by using the CSS (below detection limits). Our results also show that high dispersion of Co ₃ O ₄ corresponds to high activity in OER. The typical catalyst 4CoAS exhibits a potential of 0.73 V at the current density of 10 mA·cm ^-2 . It is superior to that of 4CoCS (0.78 V) and of the reference catalyst 4Co ₃ O ₄ /CS (0.90 V) with the same Co content. Furthermore, the catalyst 4CoAS presents quite good stability in OER and is obviously better than 4CoCS.