P‐doped g‐C3N4 as an efficient photocatalyst for CO2 conversion into value‐added materials: a joint experimental and theoretical study

• Published in: International journal of quantum chemistry Vol. 120; no. 23
• Main Authors: Ranjbakhsh, Elnaz, Izadyar, Mohammad, Nakhaeipour, Ali, Habibi‐Yangjeh, Aziz
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 05.12.2020; Wiley Subscription Services, Inc
• Subjects: adsorption; Carbon dioxide; Carbon nitride; Chemistry; CO2 reduction; Conduction bands; Density functional theory; Doping; Formic acid; g‐C3N4; Methane; Nitrogen; Phosphorus; Photocatalysis; photocatalyst; Physical chemistry; P‐doped; Quantum physics; Reduction; Valence band
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/qua.26388

The photocatalytic yield of g‐C3N4 for CO2 reduction was modified by phosphorus doping. Possible reaction pathways for CO2 reduction on the P‐doped g‐C3N4 (PCN) surface were investigated by density function theory calculations for the first time. The experimental results showed that P doping increases the carriers' lifetime, which improves the production of CH4 through the increase in the driving force of the electrons. The partial density of states of the PCN showed that the valence band maximum and conduction band minimum are composed of px, py, and, s orbitals of the N atoms and pz states of carbon, nitrogen, and phosphorus, respectively. Mechanism studies confirm that formic acid, formaldehyde, methanol, and methane are the most probable products. Methane, having positive adsorption energy, can be easily desorbed from the PCN surface, and the Gibbs activation energy of the final step is 1.98 eV. The formation of H2COOH is the rate‐determining step. Phosphorus doping of g‐C3N4 decreases electron‐hole recombination that elevates the photocatalytic activity in CO2 reduction. Based on the mechanism studies of CO2 conversion to fuels, it was confirmed that the rate‐determining step for CH4 is the formation of H2COOH.