Metal-organic Framework-driven Porous Cobalt Disulfide Nanoparticles Fabricated by Gaseous Sulfurization as Bifunctional Electrocatalysts for Overall Water Splitting.

Both high activity and mass production potential are important for bifunctional electrocatalysts for overall water splitting. Catalytic activity enhancement was demonstrated through the formation of CoS ₂ nanoparticles with mono-phase and extremely porous structures. To fabricate porous structures at the nanometer scale, Co-based metal-organic frameworks (MOFs), namely a cobalt Prussian blue analogue (Co-PBA, Co ₃ [Co(CN) ₆ ] ₂ ), was used as a porous template for the CoS ₂ . Then, controlled sulfurization annealing converted the Co-PBA to mono-phase CoS ₂ nanoparticles with ~ 4 nm pores, resulting in a large surface area of 915.6 m ²  g ^-1 . The electrocatalysts had high activity for overall water splitting, and the overpotentials of the oxygen evolution reaction and hydrogen evolution reaction under the operating conditions were 298 mV and -196 mV, respectively, at 10 mA cm ^-2 .