Recently,
the development of efficient and non-noble metal electrocatalysts
with good durability for the hydrogen evolution reaction (HER) has
attracted increasing attention. The exotic and robust metallic surface
states of topological insulators (TIs) are theoretically predicted
to enhance surface catalytic activity of overlaying catalysts, but
no experimental evidence for TIs directly used as electrocatalysts
has ever been reported. In this work, we fabricated the TI thin films
of Bi2Te3 with different thicknesses using the
molecular beam epitaxy method, and found that these thin films exhibit
high electrocatalytic activity in HER. The 48 nm Bi2Te3 thin film has the best performance, which is attributed to
its largest active area arising from the spiral growth mode of triangular
domains as revealed by atomic force microscopy imaging. Importantly,
our theoretical calculations reveal that while pure Bi2Te3 is not a good electrocatalyst, the Bi2Te3 thin films with partially oxidized surfaces or Te vacancies
have high HER activity. The existence of the corresponding surface
oxides on the Bi2Te3 thin films is supported
by our X-ray photoelectron spectroscopy data. We have also made a
direct comparison between a Bi2Te3 and a Bi2Te3:Fe thin film on their magneto-transport properties
and HER performances. Particularly, this work demonstrates that the
topological surface states play a key role in enhancing the HER performance.
Our study offers a direction to design cost-effective electrocatalysts.
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