Abstract
Summary Polymeric carbon nitrides (CNs) are regarded as the most sustainable materials for solar energy conversion via photocatalytic processes. However, the first-generation CNs suffered from imperfect charge separation and insufficient CO2 adsorption. Herein, the construction of a heterojunction material involving highly crystalline CN-nanorods with ordered alignment on graphene is delineated, which improves light harvesting, CO2 capture, and interface charge transfer. The graphene-supported 1D nano-arrays of crystalline CNs show a comparably high selectivity of CO2/N2 up to 44, with an isosteric heat of adsorption of 55.2 kJ/mol for CO2. The heterojunction material also drives the simple and efficient CO2 photoreduction in the gas phase, without the addition of any cocatalyst or sacrificial agent, even at the more relevant case of low concentrations of CO2. These findings provide a robust way for tailoring the performance of CN materials, with the aim of a practicable technological application for CO2 capture and photoreduction.
Highlights
Synthesis and Structural Analysis of 2D/1D Heterojunction of Graphene/carbon nitrides (CNs) The proof-of-concept experiments are illustrated in Scheme 1
At first melamine molecules were anchored via their amine groups onto the surface of graphene oxide (GO) through the C=O surface functionalities and hydrogen bridges
Melamine was condensed to melon and grafted onto the graphene oxide, and the GO was reduced to gain the pre-heated melon/rGO hybrid
Summary
Artificial solar-driven CO2 reduction into valuable fuels such as carbon monoxide (CO), methane (CH4), and methanol (CH3OH) based on semiconductor-mediated photocatalysis could be one of the long-term solutions to global warming and fuel shortage.[1,2,3] In many aspects, polymeric carbon nitrides (CNs) are the most promising candidates for CO2 photoreduction among various semiconductor photocatalysts, because of their metal-free nature, low-cost and environmental friendly production, and appropriate electronic properties with sufficiently strong reduction by the photoelectrons in the conduction band.[4,5,6,7] the construction of an efficient and stable photochemical system for CO2 reduction is still a challenge, because single-component semiconductors (including CNs) are less effective in exciton splitting toward single charge carriers, and the linear CO2 molecules are chemically rather inert against activation during photocatalysis.[8,9,10,11,12,13,14,15] a second semi-conductor or semi-metal, for example, graphene, is necessary to form a bulk heterojunction which accelerates exciton splitting into the two subphases, charge transfer, and surface catalytic processes promoted by single charges. The sp[2] bonded two-dimensional (2D) carbon material exhibits excellent conductivity and electron mobility and has a lower conduction band than carbon nitride, which helps to transfer and accumulate photoelectrons in the graphene subphase for surface CO2 reduction reaction,[16,17,18,19] while the carbon nitride drives the oxidation reactions. The improvement of CO2 binding for a photocatalytic material is of vital importance to improve the local CO2
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