▎ 摘　　要

The development of well-organized and low-priced photoelectrocatalysts for the clean and efficient water splitting reaction is crucial. In this context, novel nitrogen-doped graphene quantum dots (NGQDs) with high photoluminescence and upconversion emission have been synthesized as excellent light harvester. Subsequently, ordered hierarchical TiO2 nanowires were decorated with upconversion N-GQDs as a photoanode by a simple preparation method to improve the photocatalytic performance in the visible and near-infrared (NIR) regions of solar light, not otherwise absorbable by bare TiO2 nanostructures. Moreover, the enhancement of charge transfer efficiency and electron-hole separation according to the energy states of N-GQDs and TiO2 are considered for the improved photocatalytic performance of water splitting. N-GQDs/TiO2 shows superior photoelectrocatalytic (PEC) performance, achieving a photocurrent density of 3.0 mA.cm(-2) in 1.0 M KOH solution, which is eight times that of unmodified TiO2 at an applied voltage of 1.23 V vs. RHE. The high stability and photoelectrocatalytic activity of oxygen evolution reaction in the presence of newly synthesized N-GQDs are confirmed by chronoamperometry, open-circuit potential measurement, and electrochemical impedance spectroscopy. The as-fabricated photoanode provides an increased solar light harvesting from UV-Vis to NIR due to the application of newly synthesized upconversion GQDs, which increase energy conversion with an appealing perspective. (C) 2021 Elsevier Ltd. All rights reserved.