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.

Considerable efforts have been devoted recently to design and fabrication of high performance and low cost electrocatalysts for oxygen evolution reaction (OER). However, catalytic activity of current electrocatalysts is usually restricted by high onset potential and limited active sites. Herein, we fabricated three-dimensional (3D) highly ordered mesoporous Pd-Co3O4 composite materials as excellent electrocatalysts for OER in alkaline solution with high activity and stability. Three-dimensional highly ordered mesoporous Co3O4 material was firstly synthesized using mesoporous silica KIT-6 as hard template. Then, Pd-Co3O4 nanomaterials were prepared by a simple reduction method. The as-prepared 3D mesoporous Pd-Co3O4 catalysts have ordered mesoporous structure with a high surface area of 81.0 m2 g−1. Three-dimensional highly ordered mesoporous structure can facilitate diffusion and penetration of electrolyte and oxygen. Moreover, the catalysts can also keep catalyst particles in a well dispersed condition with more catalytic active sites. Electrochemical measurements reveal that the 3D mesoporous Pd-Co3O4 catalysts exhibit superior performance in alkaline solution with low onset potential (0.415 V vs. SCE) and excellent long-duration cycling stability.

Photoresponsive polymers have attracted extensive attention due to their tunable functionalities and advanced applications; thus, it is significant to develop facile in situ synthesis strategies, extend polymers family, and establish various applications for photoresponsive polymers. Herein, we develop a catalyst-free spontaneous polymerization of dihaloalkynes and disulfonic acids without photosensitive monomers for the in situ synthesis of photoresponsive polysulfonates at room temperature in air with 100% atom economy in high yields. The resulting polysulfonates could undergo visible photodegradation with strong photoacid generation, leading to various applications including dual-emissive or 3D photopatterning, and practical broad-spectrum antibacterial activity. The halogen-rich polysulfonates also exhibit a high and photoswitched refractive index and could undergo efficient postfunctionalizations to further expand the variety and functionality of photoresponsive heteroatom-containing polyesters.