Enhancing catalytic activity of tungsten disulfide through topology

Phase transition through local strain engineering is an exciting yet complex phenomenon in nanoscience for enhancing electronic, magnetic, and catalytic properties of nanomaterials. Here we report a topotactic transformation in 2H-WS2 nanobelts into 1T-WS2 nanohelices, which is mediated via an aqueous electrochemical activation method. The resulting nanohelices exhibited superior catalytic properties for HER with a low over-potential of 170 mV for an electrocatalytic current density of 10 mA/cm(2). Notably, the electrochemical stability of WS2 nanohelices increased after 20,000 cycles, where the stability of the Pt benchmark catalyst is known to decrease, thus implying WS2 nanohelices as ideal catalysts for long-term electrochemical processes. The emergence of such enhanced properties is attributed to the strain induced decrease in charge transfer resistance, enhanced per site activity and increased number of active edge sites in 1T-WS2 nanohelices. This study points the way for creating topological motifs in 2D materials with novel properties.