Integrating 3D porous morphology with efficient plasmonic Au nanoparticles in photo-responsive g-C3N4/Au hybrid photocatalyst for the enhancement of CO2 reduction

Various modification methods for graphitic carbon nitride (g-C3N4) have been widely used to improve the photocatalytic carbon dioxide reduction reaction (CO2RR) efficiency. Herein, we demonstrate a composite strategy combining three-dimensional (3D) morphology construction and plasmonic Au nanoparticle anchoring to prepare a porous g-C3N4/Au composite catalyst with effective photoresponse. In the presence of gaseous CO2 and liquid H2O without any sacrificial agent, compared with pure g-C3N4, the photocatalytic efficiency of the optimized PCN-18A was significantly improved: under the UV-Visible light irradiation of 320-780 nm, the yields of CO, CH4, and C2H4 were increased by -27.1, -17.9, and -19.3 times, respectively; under visible light irradiation from 420 to 780 nm, the yield of CO increased -48.6 times. Detailed characterization analysis and finite-difference time-domain (FDTD) simulations demonstrate that the significant increase can be mainly attributed to two reasons related to photoresponse. First, the construction of 3D porous enhanced the light absorption, and partially ordered porous regions formed inverse opal structures, causing the slow photon effect. Besides, the anchoring of Au nanoparticles facilitated electron transfer and introduced the localized surface plasmon resonance (LSPR) effect to inject hot electrons into g-C3N4. In addition, the increase of reactive sites and the enhancement of CO2 adsorption also contributed to the improvement of photocatalytic efficiency. Our work provides a new reference for the further design and optimization of photo-responsive g-C3N4-based photocatalysts.