氧掺杂氮化碳多孔纳米片高效光电催化CO2还原制甲酸

Oxygen-incorporated carbon nitride porous nanosheets for highly efficient photoelectrocatalytic CO2 reduction to formate

  • 摘要: 利用CO2作为可再生的碳源来生产高价值的燃料和化学品最近引起了全球的关注。在现有的CO2转化方法中,光电催化CO2还原反应(CO2RR)是最有效和最有前景的选择之一,它可以在模拟太阳光照和低过电位条件下实现。本研究将合成的含氧氮化碳(CN)多孔纳米片作为光电阳极,Bi2CuO4作为光电阴极,实现光电催化CO2还原生成甲酸盐。通过改变氧源,调节CN的导电性能和光电响应性能。前驱体中氧的电负性更强,因此可以提高CN的导电性能。而焙烧气氛中的氧却通过改变能带结构对光电响应性能产生了不利影响。在最优条件下,CN的光电流密度高达587 μA cm−2,CO2还原成甲酸的活性为273.56 µmol cm−2 h−1(约为常规样品的19倍)。此外,CN样品在24 h恒定的光电流下表现出良好的稳定性。本研究为实现高效的光电催化CO2还原成甲酸提供了一种新的途径,并可通过不同阴极催化剂的偶联,扩展到其他PEC反应。

     

    Abstract: Using CO2 as a renewable carbon source for the production of high-value-added fuels and chemicals has recently received global attention. The photoelectrocatalytic (PEC) CO2 reduction reaction (CO2RR) is one of the most realistic and attractive ways of achieving this, and can be realized effectively under sunlight illumination at a low overpotential. Oxygen-incorporated carbon nitride porous nanosheets (CNs) were synthesized from urea or melamine by annealing in nitrogen or N2/O2 gas mixtures. They were used as the photoanode with Bi2CuO4 as the photocathode to realize PEC CO2 reduction to the formate. The electrical conductivity and the photoelectric response of the CNs were modified by changing the oxygen source. Oxygen in CNs obtained from an oxygen-containing precursor improved the conductivity because of its greater electronegativity, whereas oxygen in CNs obtained from the calcination atmosphere had a lower photoelectric response due to a down shift of the energy band structure. The CN prepared by annealing urea, which served as the source of oxygen and nitrogen, at 550 °C for 2 h in nitrogen is the best. It has a photocurrent density of 587 μA cm−2 and an activity of PEC CO2 reduction to the formate of 273.56 µmol cm−2 h−1, which is nearly 19 times higher than a conventional sample. The CN sample shows excellent stability with the photocurrent remaining constant for 24 h. This work provides a new way to achieve efficient catalysts for PEC CO2 reduction to the formate, which may be expanded to different PEC reactions using different cathode catalysts.

     

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