MXene/graphitic carbon nitride-supported metal selenide for all-solid-state flexible supercapacitor and oxygen evolution reaction

Abstract

We report a new type of combination of rare earth metal selenides (Ce₂Se₃ and Er₂Se₃) with a Ti₃C₂T_x/S-doped graphitic carbon nitride heterostructure for bifunctional application in flexible supercapacitors and oxygen evolution reactions. The incorporation of S-doped graphitic carbon nitride in MXenes reduced the layer stacking tendency of both two-dimensional sheets and eliminated volume expansion by forming a heterostructure. Cerium and erbium rare earth metal centers induce reactive surface sites, whereas binary layers of Ti₃C₂T_x/S-doped graphitic carbon nitride provide a conducting matrix for the homogeneous growth of the metal selenides. The assembled all-solid-state flexible asymmetric supercapacitor exhibited a high specific capacitance of 60 F g⁻¹, an energy density of 10.1 W h kg⁻¹ (volumetric energy density: 0.9 mW h cm⁻³) at 2 A g⁻¹, and 100% capacitance retention after 10 000 charge–discharge cycles with good flexibility for real-time applications. Furthermore, the optimum nanohybrid showed a low overpotential of 280 mV and a Tafel slope of 99 mV dec⁻¹ with durable electrocatalytic performance. This work is the first to investigate the bifunctional energy efficiency of rare earth metal selenides grown over MXene materials.