Abstract
A comprehensive mechanistic insight into the photocatalytic reduction of CO2 by H2O is indispensable for the development of highly efficient and robust photocatalysts for artificial photosynthesis. This work presents first-principles mechanistic insights into the adsorption and activation of CO2 in the absence and presence of H2O on the (001), (010), and (110) surfaces of tantalum nitride (Ta3N5), a photocatalysts of significant technological interest. The stability of the different Ta3N surfaces is shown to dictate the strength of adsorption and the extent of activation of CO2 and H2O species, which bind strongest to the least stable Ta3N5(001) surface and weakest to the most stable Ta3N5(110) surface. The adsorption of the CO2 on the Ta3N5(001), (010), and (110) surfaces is demonstrated to be characterized by charge transfer from surface species to the CO2 molecule, resulting in its activation (i.e., forming negatively charged bent CO2−δ species, with elongated C–O bonds confirmed via vibrational frequency analyses). Compared to direct CO2 dissociation, H2O dissociates spontaneously on the Ta3N5 surfaces, providing the necessary hydrogen source for CO2 reduction reactions. The coadsorption reactions of CO2 and H2O are demonstrated to exhibit the strongest attractive interactions on the (010) surface, giving rise to proton transfer to the CO2 molecule, which causes its spontaneous dissociation to form CO and 2OH− species. These results demonstrate that Ta3N5, a narrow bandgap photocatalyst able to absorb visible light, can efficiently activate the CO2 molecule and photocatalytically reduce it with water to produce value-added fuels.
Highlights
Photocatalytic reduction of carbon dioxide (CO2 ) with water (H2 O) to produce value-added fuels such as such as CO, HCOOH, CH3 OH, and CH4 is a promising route to reduce CO2 emissions and address the global energy crisis [1,2,3,4,5]
The conventional unit cell consists of 32 atoms, where each Ta atom is bonded to six N atoms, while
The strength of adsorption and extent of CO2 activation is found to be influenced by the stability of the different
Summary
The activation and reduction of CO2 is, an energetically demanding process that involves multiple electron transfer reactions [6,7,8,9,10], highly efficient and robust photocatalysts are critical. Several photocatalysts, such as TiO2 [11,12,13], In2 O3 [14,15], Ga2 O3 [16,17], Al2 O3 [18,19], ZnO [20,21], CeO2 [22,23], ZnGe2 O4 [24], and BiVO4 [25,26], have been investigated for their performance in catalysing CO2 reduction. The stabilities of the coadsorbed CO2 –H2 O species on the various surfaces were evaluated to determine the pathways for the surface reactions involving these species, and to characterize the stability of the different reduced forms of CO2 , in particular the formate and bicarbonate species that were identified experimentally [37]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
