(521as) Carbon Quantum Dots for Sustainable Energy Conversion: Investigating Electrocatalytic and Photoelectrochemical Properties of Carbon Quantum Dots

Due to the increasing energy demand and environmental concerns, electrochemical and photoelectrochemical processes are considered as sustainable ways to produce clean energy and reduce dependence on fossil fuels. For example, (photo-)electrochemical water splitting process is one of the promising methods to yield clean hydrogen fuels. However, industrial implementation of the processes is hindered by the sluggish heterogeneous reaction kinetics and the use of costly materials. Carbon-based materials have attracted attention due to advantages including low cost, tunability in chemical structures, and stability in acidic and alkaline solutions. Among the carbon-based materials, carbon quantum dots (CQDs) are promising materials for electrocatalysts and/or photocatalysts because of the abundant active sites and large optical absorption coefficients. Significant advances have been made in designing CQDs for electrochemical and photoelectrochemical applications. However, further development is hindered by a lack of quantitative understanding of the electrocatalytic activity of CQDs at molecular-level. Here, we seek to quantify surface intermediates on CQDs with varied compositions during the electrocatalytic reactions by using scanning electrochemical microscopy (SECM). CQDs with different concentrations of heteroatoms (N, S, and P) were synthesized and deposited on the substrate electrode of SECM cell. Surface interrogation mode of SECM were used to quantitatively analyze surface intermediates at the CQD surfaces during the heterogeneous electrocatalytic water splitting reactions, oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Furthermore, we will discuss our recent efforts toward CQDs for potential photoelectrochemical water splitting applications. This work would give insight on designing cost-effective and efficient carbon-based materials for sustainable energy conversions.