Interface-engineered N-doped carbon dot/CdSe nanoconjugates as efficient Bi-functional electrocatalysts in alkaline media

Abstract

Electrochemical water oxidation is a cornerstone of sustainable energy technologies, yet its sluggish kinetics demand the design of high-performance, low-cost electrocatalysts. In this study, a rationally designed cost-effective carbon quantum dots/cadmium selenide (CQDs/CdSe) nanocomposite was demonstrated as an efficient electrode material for integrated hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). Furthermore, the hydrothermally synthesized nanocomposite exhibits enhanced charge separation, strong interfacial interactions and a larger number of electroactive sites, leading to improved ion transport and superior conductivity. The CQDs/CdSe nanocomposite revealed low overpotentials of 95 mV and 170 mV for the HER and OER, respectively, at a current density of 10 mA cm⁻², with corresponding Tafel slopes of 43 mV dec⁻¹ and 63 mV dec⁻¹. The catalyst also demonstrated excellent stability over 50 hours at 50 mA cm⁻². A proof-of-concept device with a two-electrode electrolysis set-up was configured using CQDs/CdSe as both the anode and cathode. This device achieved a current density of 10 mA cm⁻² at 1.77 V, and real-time hydrogen and oxygen evolution was successfully illustrated using a commercial 9-V battery in an H-cell setup. This work highlights the potential of CQD-based hybrid nanostructures as scalable, earth-abundant, intrinsic electrocatalysts for sustainable hydrogen generation.