Designing multifunctional Nb${}_2$O${}_5$ rods with ZnO modified g-C${}_3$N${}_4$ hybrid material for energy storage and hydrogen evolution

The design of multifunctional materials for energy storage and conversion systems is vital in addressing present global energy issues. In this work, we have prepared a highly active and economical hybrid material comprising ZnO and Nb${}_2$O${}_5$, integrated with g-C${}_3$N${}_4$ (Nb@ZGCN) through the simple chemical method followed by calcination process. The resultant Nb@ZGCN electrode delivered a specific capacitance of 122.3 F g${}^{-1}$ at a current density of 1 A g${}^{-1}$ and maintained 71% of its initial value at a current density of 4 A g${}^{-1}$ in a 6 M KOH electrolyte. This hybrid electrode exhibited superb cyclic stability of 105% even after 2000 cycles at 4 A g${}^{-1}$ with an increased coulomb efficiency than the first cycle which is close to 100%. Additionally, the prepared hybrid material was further applied for electrocatalytic hydrogen evolution reaction (HER), delivering a small overpotential of 252.1 mV to achieve a current rate of 10 mA cm${}^{-2}$ along with long-term durability in a 1 M KOH medium. The synergistic interaction between the ZnO, Nb${}_2$O${}_5$ and graphitic carbon nitride in the hybrid structure leads to abundant electroactive sites that remarkably improve the supercapacitive and HER activities. These results suggest that the developed hybrid material can be further exploited as an electrode material for supercapacitor and water splitting applications.