Insights into the regulation of energy storage behaviors of antimonene in aqueous electrolytes.

• Antimonene show a mixture of surface-controlled and battery-like responses in acid. • Power-law and kinetics simulation further confirm the energy storage mechanism. • EQCM and DFT reveal that hydrated H +can access the inner surface sites of antimonene. • The as-prepared ASC exhibits wide operating voltage and great cycling performance. Advanced secondary energy storage technologies and key components are crucial to the efficient use of energy resources. Layered antimonene can facilitate ions transport and intercalation. However, the electrochemical mechanism of antimonene is very much a gray area. Herein, we show that the electrolyte ions can make appreciable differences in the energy storage behavior of antimonene. Accordingly, a high value of 599 F g −1 can be obtained by scanning antimonene electrode in 1 M H 2 SO 4 at a rate of 5 mV s −1, which is more than twice the capacitance of those KOH, LiOH and LiCl based electrolyte systems. Systematic investigation including kinetics simulation and extrapolation of surface charge suggests a mixture of surface-controlled and battery-like Faradaic responses of antimonene in acid electrolyte. Electrochemical quartz crystal microbalance (EQCM) combined with first-principles calculation further reveals that hydrated H + is expected to access the "inner" surface sites of antimonene and thus insert or intercalate into the antimonene nanosheets. Notably, an asymmetric supercapacitor composed of antimonene positrode and carbon nanotube negatrode exhibits a wide operating voltage of 1.8 V, a relatively high energy density of 46 Wh Kg−1 at a power density of 450 W Kg−1 and great cycling performance (capacitance retention of up to 112.7% after 5000 cycles, 1.5 A g −1). The paper offers fundamental insights into the influence of electrolyte ions on the electrochemical behavior of 2D Xenes and pushes back the frontiers of designing energy storage systems. [Display omitted] [ABSTRACT FROM AUTHOR]