Selective Photocatalytic Reduction of CO₂ to CO Mediated by Silver Single Atoms Anchored on Tubular Carbon Nitride

Abstract

Artificial photosynthesis is a promising strategy for converting carbon dioxide (CO2) and water (H2O) into fuels and value‐added chemical products. However, photocatalysts usually suffered from low activity and product selectivity due to the sluggish dynamic transfer of photoexcited charge carriers. Herein, we describe anchoring of Ag single atoms on hollow porous polygonal C3N4 nanotubes (PCN) to form the photocatalyst Ag1@PCN with Ag−N3 coordination for CO2 photoreduction using H2O as the reductant. The as‐synthesized Ag1@PCN exhibits a high CO production rate of 0.32 μmol h−1 (mass of catalyst: 2 mg), a high selectivity (>94 %), and an excellent stability in the long term. Experiments and density functional theory (DFT) reveal that the strong metal–support interactions (Ag−N3) favor *CO2 adsorption, *COOH generation and desorption, and accelerate dynamic transfer of photoexcited charge carriers between C3N4 and Ag single atoms, thereby accounting for the enhanced CO2 photoreduction activity with a high CO selectivity. This work provides a deep insight into the important role of strong metal–support interactions in enhancing the photoactivity and CO selectivity of CO2 photoreduction.

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

“…In addition, the in situ DRITFs of CN@CQD (Figure S16) exhibited similar infrared absorption of various crucial intermediates in the 1000–1500 cm –1 region. However, the stretching vibration signal of the COOH* group at 1597 cm –1 of CN@CQD was noticeably weaker than that of CN-CQD . Moreover, in the infrared absorption region of both CO 2 and H 2 O, the signal intensity of CN@CQD was also weaker than that of CN-CQD.…”

“…The peaks observed at 1362 and 1597 cm –1 can be attributed to the COOH* signal, which is considered a crucial intermediate species in the conversion of CO 2 to CO or CH 4 . Furthermore, the vibration signals at 1098 and 1156 cm –1 originate from CHO* and CH 3 O* species, respectively, which are important intermediates involved in CH 4 formation. , Moreover, intermediates including b-CO 3 2– (1283 cm –1 ), m-CO 3 2– (1508 cm –1 ), and HCO 3 * (1436 cm –1 ) were also detected . In addition, the signals of H 2 O (about 1648 and 3425 cm –1 ) and CO 2 (2335 cm –1 ) exhibited negative values, , indicating the consumption of H 2 O as a proton source and CO 2 as a raw material in the photoreaction system.…”

“…However, the stretching vibration signal of the COOH* group at 1597 cm −1 of CN@CQD was noticeably weaker than that of CN-CQD. 62 Moreover, in the infrared absorption region of both CO 2 and H 2 O, the signal intensity of CN@CQD was also weaker than that of CN-CQD. Therefore, the findings suggest that the amide covalent bond plays an influential role in facilitating the production of COOH*, which subsequently improves the performance of the CN-CQD photocatalytic reduction of CO 2 .…”

“…60 Furthermore, the vibration signals at 1098 and 1156 cm −1 originate from CHO* and CH 3 O* species, respectively, which are important intermediates involved in CH 4 formation. 61,62 Moreover, intermediates including b-CO 3 2− (1283 cm −1 ), m-CO…”

Single‐atom materials: The application in energy conversion

“…In the process of photocatalysis, the process is divided into three main parts: light harvesting, charge transfer, and surface reaction. [ 72–76 ] The first thing that needs to be considered is the light efficiency during the reaction, which is greatly influenced by the band structure of the catalysts. The substrates of the SAMs often act as the provider, which can generate plenty of electron–hole pairs for the latter reaction.…”