Single-atom Zn for boosting supercapacitor performance

Single-atom metal-incorporated carbon nanomaterials (CMs) have shown great potential towards broad catalytic applications. In this work, we show that N-doped porous CMs embedded with redox-able Zn atoms exhibit superior capacitive performance. High Zn (~ 2.72 at.%)/N (~ 12.51 at.%) doping were realized by incorporating Zn²⁺ and benzamide into the condensation and carbonization of formamide and subsequent annealing at 900 °C. The Zn and N species are mutually benefited during the formation of ZnN₄ motif. The as-obtained Zn₁NC material affords a very large capacitance of 621 F·g⁻¹ (at 0.1 A·g⁻¹), superior rate capability (~ 65% retention at 100 A·g⁻¹), and excellent cycling stability (0.00044% per cycle at 10 A·g⁻¹). These merits are attributed to the high Zn/N loading, atomic Zn-boosted pseudocapacitive behavior, large specific surface area (~ 1,085 m²·g⁻¹), and rich pore hierarchy, thus ensuring both large pseudo-capacitance (e.g., ~ 37.9% at 10 mV·s⁻¹) and double-layer capacitance. Besides of establishing a new type of high Zn/N-loading carbon materials, our work uncovers the capacitive roles of atomically dispersed metals in CMs.