The separation and transfer of charge carriers, adsorption of CO2 molecules, and desorption of product molecules are crucial factors that affect the CO2 photoreduction process. Herein, we demonstrate the significant facet effect of Pd cocatalyst toward CO2 photoreduction over graphitic carbon nitride (g-C3N4). The surface atomic structure of Pd cocatalyst can be precisely controlled by adjusting the amount of {111} and {100} facets to modulate the interfacial charge carrier transfer, CO2 adsorption and CH3OH desorption. It is shown that the tetrahedral Pd nanocrystals with exposed {111} facets function as a more efficient cocatalyst as compared to cubic Pd nanocrystals with exposed {100} facets, which is reflected by enhancing the CO2 photoreduction over graphitic carbon nitride. The origin of such remarkable shape induced effect is explained on the basis of experimental studies of charge transfer dynamics and the atomic-scale DFT modeling of CO2 adsorption and CH3OH desorption. (C) 2017 Elsevier Inc. All rights reserved.