Hollow TiO@CoS Core-Branch Arrays as Bifunctional Electrocatalysts for Efficient Oxygen/Hydrogen Production.

Designing ever more efficient and cost-effective bifunctional electrocatalysts for oxygen/hydrogen evolution reactions (OER/HER) is greatly vital and challenging. Here, a new type of binder-free hollow TiO@CoS core-branch arrays is developed as highly active OER and HER electrocatalysts for stable overall water splitting. Hollow core-branch arrays of TiO@CoS are readily realized by the rational combination of crosslinked CoS nanoflakes on TiO core via a facile and powerful sulfurization strategy. Arising from larger active surface area, richer/shorter transfer channels for ions/electrons, and reinforced structural stability, the as-obtained TiO@CoS core-branch arrays show noticeable exceptional electrocatalytic performance, with low overpotentials of 240 and 139 mV at 10 mA cm as well as low Tafel slopes of 55 and 65 mV Dec for OER and HER in alkaline medium, respectively. Impressively, the electrolysis cell based on the TiO@CoS arrays as both cathode and anode exhibits a remarkably low water splitting voltage of 1.56 V at 10 mA cm and long-term durability with no decay after 10 d. The versatile fabrication protocol and smart branch-core design provide a new way to construct other advanced metal sulfides for energy conversion and storage.