Highly Effective Electrochemical Exfoliation of Ultrathin Tantalum Disulfide Nanosheets for Energy-Efficient Hydrogen Evolution Electrocatalysis.

Developing highly efficient transition metal dichalcogenide electrocatalysts would be significantly beneficial for the electrocatalytic hydrogen evolution reaction (HER) from water splitting. Herein, we reported novel ultrathin tantalum disulfide nanosheets (TaS2 NSs) prepared by electrochemically exfoliating bulk TaS2 with an alternating voltage in an acidic electrolyte. The obtained TaS2 NS electrocatalyst possessed an ultrathin structure with a lateral size of 2 μm and a thickness of ∼3 nm. Owing to the unique 2D structure, the achieved TaS2 NSs displayed remarkable electrocatalytic activity toward the HER by a small overpotential of 197 mV at 10 mA cm-2 and a small Tafel slope of 100 mV dec-1 in acidic solution, much lower than those of TaS2 (>547 mV and 216 mV dec-1, respectively) and other reported TaS2-based HER electrocatalysts. Furthermore, highly efficient full water splitting could be realized with two electrodes in which TaS2 NSs acted as the cathode while Ir/C served as the anode, with help of two AA size batteries or solar cells. By replacing the oxygen evolution reaction with the urea oxidation reaction (UOR), bifunctional TaS2 NSs enabled an energy-effective HER process in the cathode and UOR process in the anode with decreased applied potential.