Solvothermal Synthesis of a High Supercapacitive Humate–NiCo–LDH Composite Material Derived from the Humate–ZIF-67 Template

Metal organic frameworks (MOFs) have good porosity and adjustable morphology, which are always used as excellent sacrificial templates to derive high-performance layered double hydroxides (LDHs). Here, a humate-based ZIF-67 (HA–ZIF-67) template is first prepared by a natural precipitation method using humates as a substrate. And a humate-based NiCo–LDH (HA–NiCo–LDH) composite material is then successfully prepared via a solvothermal approach with ethanol as a protic solvent. Due to the special composite structure including NiCo–LDH nanocages assembled by interlaced nanosheets, suitable incorporation of layered humate substrate with graphitized microdomains and rich mesopores, the HA–NiCo–LDH exhibits a low resistance during the ionic diffusion, charge transfer, and electron conduction process, a large capacity of 1083 C g–1 (0.5 A g–1), and an excellent cycle stability with a capacity retention of 77% over 10000 GCD loops at 5 A g–1. The assembled asymmetric supercapacitor of the HA–NiCo–LDH//AC also has a decent capacity retention of 52% of initial value with the current density increasing from 0.5 to 10 A g–1, and a large energy density of 44.9 Wh kg–1 at a power density of 348 W kg–1. Its capacity retention is still high to 98% at 5 A g–1 over 5000 GCD loops. Hence, the moderate incorporation of humates is of great significance for practical applications of the NiCo–LDH in supercapacitors.