Tuning the active plane and crystallinity of GaN microcrystals for high-performance supercapacitors through potassium nitrate-mediated synthesis

The surface atomic structure and crystallinity have an important effect on the electrochemical energy storage of electrode materials , in addition to the surface chemistry and textural properties. We report here for the first time that the surface atomic structure and crystallinity of GaN , a renowned electrode material for energy storage, can be tuned by controlling the annealing time via potassium nitrate-mediated synthesis. The underlying mechanism for GaN microcrystals with enhanced intensity ratios of I (002)/(100) and I (101)/(100) manifesting excellent rate performance has been revealed by theoretical computations. The energy storage mechanism and electrode kinetics of the GaN electrodes have been clarified. In addition, the GaN microcrystals-based symmetric supercapacitors empowered by 52 wt% H 3 PO 4 can deliver an output voltage of 1.5 V and volumetric specific energy of 11.6 and 40.2 W h L −1 at a specific power of 392.2 W L −1 when operating at −60 and 60 °C, respectively, with electrode material on a commercial loading level.