Amide Covalent Bonding Engineering in Heterojunction for Efficient Solar-Driven CO₂ Reduction

Inefficient charge separation and slow interfacial reaction dynamics significantly hamper the efficiency of photocatalytic CO₂ reduction. Herein, a facile EDC/NHS-assisted linking strategy was developed to enhance charge separation in heterojunction photocatalysts. Using this approach, we successfully synthesized amide-bonded carbon quantum dot-g-C₃N₄ (CQD-CN) heterojunction photocatalysts. The formation of amide covalent bonds between CN and CQDs in the CN-CQD facilitates efficient carrier migration, CO₂ adsorption, and activation. Exploiting these advantages, the CN-CQD photocatalysts exhibit high selectivity with CO and CH₄ evolution rates of 79.2 and 2.7 μmol g^-1 h^-1, respectively. These rates are about 1.7 and 3.6 times higher than those of CN@CQD and bulk CN, respectively. Importantly, the CN-CQD photocatalysts demonstrate exceptional stability, even after 12 h of continuous testing. The presence of the COOH* signal is identified as a crucial intermediate species in the conversion of CO₂ to CO. This study presents a covalent bonding engineering strategy for developing high-performance heterojunction photocatalysts for efficient solar-driven reduction of CO₂.