Sub-5 nm edge-rich 1T′-ReSe2 as bifunctional materials for hydrogen evolution and sodium-ion storage

Highlights: • Sub-5 nm 1T'-ReSe₂ nanoflakes on CNT surface were synthesized via CVD method. • The highly active edge site of 1T'-ReSe₂ in HER was revealed by DFT and experiments. • The kinetics of first cycle of 1T'-ReSe₂ as SIBs anode was unveiled by in situ XAS. -- Abstract: The rhenium-based transition metal dichalcogenides (TMDs), as new members in the TMDs family, have raised great interests recently. Due to the anisotropic structure and unique photoelectric properties, they have potential applications for electrochemical energy conversion and storage. In this work, we performed density functional theory (DFT) calculations on pristine 1T′-ReSe₂ toward hydrogen evolution reaction (HER). The results indicated that the Gibbs free energy of the 1T′-ReSe₂ edge site for HER could be as small as 0.01 eV, superior to other reported TMDs. Experimentally, we developed a strategy to fabricate sub-5 nm sized 1T′-ReSe₂ nanoflakes on carbon nanotubes. Such a small size for the nanoflakes brought abundant edge exposure, which boosted the catalytic activity in the HER. Specifically, the 1T′-ReSe₂ nanoflakes needed only 23 and 60 mV overpotentials to achieve −1 and −10 mA cm⁻² current densities, along with a low Tafel slope of 37 mV dec⁻¹ and a high exchange current density of 0.3 mA cm⁻². The edge-rich and layered 1T′-ReSe₂ was also explored as an anode for sodium ion battery. The in operando X-ray absorption near edge structure (XANES) technique was applied to investigate the TMD behavior in real-time during the sodiation/desodiation process. The in situ results revealed that the nanosized 1T′-ReSe₂ is electrchemically reversible during discharge/charge cycles. The electrochemical test results demonstrated that 1T′-ReSe₂ could be a promising anode material for alkaline batteries.