Tuning Germanane Band Gaps via Cyanoethyl Functionalization for Cutting-Edge Photoactive Cathodes: Photoenhanced Hybrid Zinc-Ion Capacitor Evaluation

Energy harvesting and storing by dual-functional photoenhanced (photo-E) energy storage devices are being developed to battle the current energy hassles. In this research work, our investigations on the photoinduced efficiency of germanane (Ge–H) and its functionalized analogue cyanoethyl (Ge–C2–CN) are assessed as photocathodes in photo-E hybrid zinc-ion capacitors (ZICs). The evaluated self-powered photodetector devices made by these germanene-based samples revealed effective performances in photogenerated electrons and holes. The photo-E ZICs findings provided a photoinduced capacitance enhancement of ∼52% (for Ge–H) and ∼26% (for Ge–C2–CN) at a scan rate of 10 mV s–1 under 100 mW cm–2 illumination with 435 nm wavelength. Further characterizations demonstrated that the photo-E ZIC with Ge–C2–CN supply higher specific capacitance (∼6000 mF g–1), energy density (∼550 mWh kg–1), and power density (∼31,000 mW kg–1), compared to the Ge–H. In addition, capacitance retention of photo-E ZIC with Ge–C2–CN is ∼91% after 3000 cycles which is almost 6% greater than Ge–H. Interestingly, the photocharging voltage response in photo-E ZIC made by Ge–C2–CN is 1000 mV, while the photocharging voltage response with Ge–H is approximately 970 mV. The observed performances in Ge–H-based photoactive cathodes highlight the pivotal role of such two-dimensional materials to be applied as single architecture in new unconventional energy storage systems. They are particularly noteworthy when compared to the other advanced photo-E supercapacitors and could even be enhanced greatly with other suitable inorganic and organic functional precursors.