Flower-shaped and sea urchin-shaped structures coexisting in cobalt-based phosphate and oxides achieve efficient electrochemical overall water electrolysis.

Active site engineering for electrocatalysts is an essential strategy to improve their intrinsic electrocatalytic capability for practical applications and it is of great significance to develop a new excellent electrocatalyst for overall water splitting. Here, Co 3 O 4 /nickel foam (NF) and Co 2 (P 4 O 12)/NF electrocatalysts with flower-shaped and sea urchin-shaped structures are synthesized by a simple hydrothermal process and followed by a post-treatment method. Among them, Co 2 (P 4 O 12)/NF shows good catalytic activity for hydrogen evolution reaction (HER), and at the current density of 10 mA cm−2, the overpotential is only 113 mV Co 3 O 4 /NF exhibits good catalytic activity for oxygen evolution reaction (OER), and the overpotential is 327 mV at 20 mA cm−2. An alkaline electrolyzer with Co 3 O 4 /NF and Co 2 (P 4 O 12)/NF catalysts respectively as anode and cathode displays a current density of 10 mA cm−2 at a cell voltage of 1.59 V. This work provides a simple way to prepare high efficient, low cost and rich in content promising electrocatalysts for overall water splitting. [Display omitted] • Self-supporting materials avoid the use of adhesives. • Flower-shaped and sea urchin-shaped structures increase number of active sites. • Unique structure facilitates electrolyte immersion and separation of bubbles. • Oxygen vacancy-rich Co 3 O 4 can effectively catalyze OER. • Self-supporting Co 3 O 4 /NF and Co 2 (P 4 O 12)/NF display good electrochemical stability. [ABSTRACT FROM AUTHOR]