Fabrication and electrochemical kinetics studies of reduced carbon quantum dots- supported palladium nanoparticles as bifunctional catalysts in methanol oxidation and hydrogen evolution reactions.

• CQDs were synthesized by facile and affordable electrochemical method • One step electrochemical method was employed to synthesis and deposition of electrodes. • CQDs caused to enhanced active surface area for deposition of metal nanoparticles. • The Pd-NPs/RCQD nanocomposite, offers promising option for wide catalytic applications such as high stability, low activation energy, high current density and good electric conductivity for MOR and HER. Glassy carbon electrode, GCE, is decorated with an electrochemically-deposited layer of reduced carbon quantum dots, RCQDs. The Pd nanoparticles are then electrodeposited on RCQDs and the Pd-NPs/RCQDs/GCE is fabricated. The fabricated electrodes are characterized by some characterization techniques. The electrocatalytic performance of the electrodes for methanol oxidation reaction, MOR, and hydrogen evolution reaction, HER, are investigated using different electrochemical measurement techniques in alkaline and acidic media, respectivly. Cyclic voltammetry, CV, Linear sweep voltammetry, LSV, Chronoamperometry, CA, and electrochemical impedance spectroscopy, EIS, measurements are used to evaluate the bifunctional catalytic behavior of the Pd-NPs/RCQDs/GCE. All results are compared with Pd-NPs/GCE and the effect of decorating the GCE substrate with RCQDs is discussed. The results indicate that modification of GCE with a layer of RCQDs increases the active surface area from 0.12 for Pd-NPs/GCE to 0.22 cm2 for Pd-NPs/RCQDs/GCE. Also E onset and EIS parameters are calculated. [ABSTRACT FROM AUTHOR]