Few-layer tellurium represents the two-dimensional (2D) form of tellurium crystal with the majority of the Te atoms exposed on its surface. Recent studies demonstrated that 2D Te has good environmental stability and high charge carrier mobility, making it suitable electrocatalyst support to host active sites and assist electron transfer between the electrode and the sites [1]. Yet, its mass production for electrocatalysis application remains challenging.

In this study, we present a simple cathodic exfoliation method to exfoliate commercially available Te crystal directly into few-layer tellurium with exceptionally high yield [2] (see Figure 1A). Using alkaline aqueous electrolyte (1.0 M KOH), Te nanosheets with the thickness of 7~10 nm and lateral size of 1~4 µm were produced at an applied potential of −0.42 V (vs. RHE). Combining in situ Raman spectroscopy and ex situcharacterization results, we were able to reveal the exfoliation mechanism, where the in situ generated ditelluride (Te₂²⁻) anions on the nanosheets played the critical role of separating nanosheets from the bulk crystal (see Figure 1B).

At the presence of transition metal ions in the electrolyte, such as Pt²⁺ and Ni²⁺, simultaneous surface doping of Te nanosheets was enabled by the interaction between Te₂²⁻ anions and metal ions, producing Pt/Ni-doped Te with tunable doping level. Such doped nanosheets exhibited high stability and hydrogen evolution reaction (HER) activity. Particularly at high potential, Pt-doped Te nanosheets outperformed both polycrystalline Pt and commercial Pt/C catalysts (see Figure 1C). We suggested a collaborative hydrogen production mechanism via Volmer–Heyrovsky pathway to justify such unusual activity. In short, at HER conditions, the surface Te atoms of Pt-doped Te nanosheets are reduced to Te₂²⁻ anions. Such species can help attract protons and assist their transfer to adjacent Pt atoms, where the protons are reduced to form hydrogen (see Figure 1D).

Figure 1 (A) Experimental setup and photos of the electrochemical exfoliation of Te crystal; (B) Exfoliation mechanism; (C) HER performance and relative energy of Pt-doped Te with various doping levels; (D) Collaborative HER mechanism.

Reference:

1. Shi, Z.; Cao, R.; Khan, K.; Tareen, A. K.; Liu, X.; Liang, W.; Zhang, Y.; Ma, C.; Guo, Z.; Luo, X.; Zhang, H., Nano-Micro Lett. 2020, 12 (1), 99.
2. Zheng, W.; Li, Y.; Liu, M.; Lee, L. Y. S., Small 2021, 17 (18), e2007768.