The team of Professor Shen Shengping from the School of Aerospace Engineering of Xi’an Jiaotong University (XJTU) has designed a tungsten (W)@tungsten disulfide (WS2) core-shell nanosphere structure that can be used to improve the electrical and chemical properties of WS2. The electrocatalytic hydrogen evolution performance of WS2 surpasses most similar materials.

The study found that the highly curved WS2 nanosheets can greatly widen the interlayer spacing, which leads to strong lattice deformation, which in turn exposes more atomic vacancies and defects. 

In addition to serving as the substrate for the bending growth of WS2 nanosheets, the core of metal W increases the overall conductivity of the catalytic material by a factor of 4.5.

On the basal surface of the nanosphere, the Gibbs free energies of hydrogen and sulfur (H-S) and hydrogen and tungsten (H-W) are 0.357eV and -0.145eV respectively. Compared with the flat W@WS2 heterostructure, the combination of hydrogen on the curved spherical shell is closer to the equilibrium energy. In addition, the W site on the WS2 spherical shell exhibited the strongest catalytic activity.

The study also found that the microstructure design helps regulate and control the hydrogen adsorption structure, heterogeneous interface structure, and the density of states near the Fermi level, thereby achieving faster and more efficient hydrogen release and electron adsorption.

The nanosphere aggregate nanoporous van der Waals heterostructure proposed in this study can solve the challenge of ion embedding channel closure caused by traditional nanosheet stacking.

Experiments show that the reaction potential of the catalyst is 161mV (at 10 mA/cm2), and it has excellent stability when reacting in a strong acid electrolyte (lasting 100 h). It also has the smallest Tafel slope (34.5 mV/dec) among similar materials and the largest electrochemical reaction area (62.2 mF/cm2).

This work puts forward a research idea to realize multi-site, high-conductivity TMDs, which will not only help promote the development of electrocatalytic hydrogen evolution technology but also enrich the selection of electrode materials for batteries, electrochemical capacitors and drivers.

The research work was published in the internationally renowned academic journal, Journal of Materials Chemistry A, with the title "Facilitating electrocatalytic hydrogen evolution via multifunctional tungsten@tungsten disulfide core-shell nanospheres".

The first unit of the thesis is the School of Aerospace Engineering, of Xi'an Jiaotong University, and the first author is doctoral student Ji Liang. This work was funded by major projects of the National Natural Science Foundation of China.

Link to the paper: https://pubs.rsc.org/en/content/articlelanding/2021/ta/d1ta01094h/unauth#!divAbstract