N-doped C dot/CoAl-layered double hydroxide/g-C3N4 hybrid composites for efficient and selective solar-driven conversion of CO2 into CH4

Converting CO2 into value-added fuel by utilizing abundant solar energy could in principle minimize fossil fuel consumption and anthropogenic CO2 emissions. However, developing catalytic systems with high selectivity and efficiency is necessary for photocatalytic CO2 conversion. Here we report the fabrication of a N-doped C dot/CoAl-layered double hydroxide/g-C3N4 (NCD/LDH/CN) hybrid heterojunction photocatalyst for high efficiency and selectivity reduction of CO2 with water into CH4 under simulated-solar-light illumination. The NCD/LDH/CN hybrid photocatalyst demonstrated remarkable CH4 production with an optimum rate of 25.69 μmol g−1 h−1, an apparent quantum yield of 0.62%, and 99% selectivity for CH4. This NCD/LDH/CN hybrid system also exhibited exceptional stability and durability during consecutive test cycles with no apparent change in activity. The high activity and stability of the NCD/LDH/CN hybrid toward CO2 photoreduction is essentially attributable to the strong synergy among the NCD, LDH, and CN constituents, which hinder charge recombination by accelerating charge transportation processes, together with the favorable properties such as broad optical response and good CO2 adsorption capability. We explored the role of the NCDs in the NCD/LDH/CN hybrid system as a metal-free co-catalyst for the efficient and selective production of CH4 from CO2 photoreduction. Thus, the present report provides new insights into the rational fabrication of noble-metal-free photocatalysts for efficient and selective sustainable hydrocarbon production from photocatalytic reduction of CO2. [Display omitted] •N-doped C dot/CoAl-LDH/g-C3N4 hybrid heterojunction was fabricated for the first time.•Hybrid heterojunction displayed exceptional CO2 reduction performance to generate CH4.•Rapid charge transfer owing to intimate interfacial contact contributed to high activity.•Hybrid catalyst displayed high stability and durability during consecutive test cycles.•NCDs played multiple roles for the efficient and selective production of CH4 from CO2 reduction.