Advantages of nitrogen-doped graphene quantum dots as a green sensitizer with ZnO nanorod based photoanodes for solar energy conversion

• Undoped and nitrogen-doped graphene quantum dots (N-GQDs) were synthesized
• Photoelectrochemical properties of N-GQD sensitized ZnO nanorods was investigated
• Sensitized nanorods demonstrated superior photoconversion efficiency and incident photon to current conversion efficiency
• N-GQDs exhibited better photoelectrochemical behavior due to strong chemical bonding and lower interfacial resistance.

Graphene quantum dots (GQDs) and nitrogen-doped graphene quantum dots (N-GQDs) have been synthesized by a hydrothermal process. Optical absorption study revealed strong ultraviolet photoabsorption for both GQDs. An additional broad absorption band in the visible region has been observed for N doped GQDs. GQDs and N-GQDs both are highly luminescent and exhibit excitation dependent emission behaviors. Photoelectrochemical properties of GQD and N-GQD sensitized ZnO nanorods have been investigated in details. GQD modified nanorod photoanodes demonstrated superior photoconversion efficiency and incident photon to current conversion efficiency (IPCE) than pristine ZnO nanorods. N-GQD sensitized nanorods exhibited better photoelectrochemical properties than pristine GQD due to higher visible photoabsorption and lower interfacial resistance.

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