Preparation of 3D g-C3N4 foam supported Cu(OH)2 nanosheets for photocatalytic CO2 reduction

To optimize the gas transfer, adsorption and photo-generated charge separation in the process of photocatalytic CO2 reduction by g-C3N4, the photocatalytic materials were designed from the aspects of foam pore structure and heterojunction construction. The typical g-C3N4 foam was first constructed using surfactant foaming method, and then Cu(OH)2 nanosheets were loaded to prepare the Cu(OH)2/CNF composites with projects of electroless copper plating and hydrogen oxidation treatment. The structure and photocatalytic properties of the as-prepared samples were investigated. The results show that g-C3N4 foam and Cu(OH)2/CNF all demonstrate developed structures with 3D micron pore frameworks, which is conducive to improving CO2 diffusion and adsorption at dynamics during gas-solid catalytic process. The adsorption amounts of CO2 for g-C3N4 foam and Cu(OH)2/CNF are respectively 3.97 cm3/g and 3.59 cm3/g, which are 2.96 times and 2.68 times respectively higher than that of pure g-C3N4 powder. Moreover, many Cu(OH)2 nanosheets are also formed in the Cu(OH)2/CNF samples which provide a way to simultaneously broaden light absorption and form heterojunction between g-C3N4 and Cu(OH)2. This heterojunction can accelerate the separation of photo-generated e--h+ and make photo-generated electrons transfer from g-C3N4 to Cu(OH)2. As a result, the Cu(OH)2/CNF has demonstrated optimal photocatalytic activity with CO production rate at 11.041 μmol·g-1·h-1, which is 2.76 times and 6.83 times respectively higher than that of g-C3N4 foam and g-C3N4 powder.