Temperature-Driven Structural Evolution in N-Doped Carbon Dots for Tailored Electrocatalytic CO₂ER-HER Pathways

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Electrocatalytic conversion of CO2 and water splitting are crucial for sustainable energy.
• Nitrogen-doped carbon dots (NCDs) are emerging as promising electrocatalysts.
• Controlling NCD structure is key to tuning their catalytic selectivity.

Purpose of the Study:

• To investigate the tunable electrocatalytic activity of NCDs for CO2 reduction (CO2ER) and hydrogen evolution reaction (HER).
• To correlate the synthesis temperature-dependent structural evolution of NCDs with their catalytic performance.
• To understand the selectivity of NCDs towards CO2ER versus HER.

Main Methods:

• Synthesis of NCDs via thermolysis of citric acid and urea at varying temperatures (140–400 °C).
• Characterization using microscopic and spectroscopic techniques.
• Electrochemical evaluation using Linear Sweep Voltammetry (LSV) and Chronoamperometry.

Main Results:

• NCDs synthesized at 300 °C exhibited highest CO2ER activity (4.3 mA cm-2) and Faradaic efficiency (FE) of 69.96% for CO2 reduction products.
• NCDs synthesized at 400 °C showed high selectivity for HER (FE of 64.82%) with poor CO2ER activity (FE of 30.18%).
• Structural transition from molecular clusters to graphitic domains with increasing temperature influenced catalytic behavior.

Conclusions:

• Tunable electrocatalytic activity for CO2ER and HER is achievable by controlling NCD synthesis temperature.
• NCD structure and nitrogen bonding environment dictate selectivity towards CO2ER or HER.
• NCDs offer a versatile platform for developing selective electrocatalysts for energy applications.