Li Yang, Li Baihai, Zhang Dainan, Cheng Lei, Xiang Quanjun
State Key Laboratory of Electronic Thin Film and Integrated Devices, School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China.
College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070, P.R. China.
ACS Nano. 2020 Aug 25;14(8):10552-10561. doi: 10.1021/acsnano.0c04544. Epub 2020 Aug 3.
Single metal atom photocatalysts have received widespread attention due to the rational use of metal resources and maximum atom utilization efficiency. In particular, N-rich amorphous g-CN is always used as a support to anchor single metal atoms. However, the enhancement of photocatalytic activity of g-CN by introducing a single atom is limited due to the bulk morphology and the excess defects of amorphous g-CN. Here, we report crystalline g-CN nanorod supported copper single atoms by molten salts and the reflux method. The prepared single Cu atoms/crystalline g-CN photocatalyst (Cu-CCN) shows highly selective and efficient photocatalytic reduction of CO under the absence of any cocatalyst or sacrificial agent. The introduction of single Cu atoms can be used as the CO adsorption site, thus increasing the adsorption capacity of Cu-CCN samples to CO. Theoretical calculation results show that reducing CO to CH on Cu-CCN samples is an entropy-increasing process, whereas reducing CO to CO is an entropy-decreasing process. As a result, the Cu-CCN samples exhibited enhanced photocatalytic CO reduction with nearly 100% selective photocatalytic CO to CO conversion. The mechanism of photocatalytic CO reduction over Cu-CCN samples was proposed based on Fourier transform infrared spectra, X-ray absorption spectroscopy, and density functional theory calculation. This work provides an in-depth understanding of the design of photocatalysts for enhancing active sites of the reactants.
单金属原子光催化剂由于金属资源的合理利用和最大原子利用效率而受到广泛关注。特别是，富氮非晶态g-CN总是被用作锚定单金属原子的载体。然而，由于非晶态g-CN的体相形态和过多缺陷，通过引入单原子来提高g-CN的光催化活性是有限的。在此，我们报道了通过熔盐法和回流法制备的结晶g-CN纳米棒负载铜单原子。所制备的单铜原子/结晶g-CN光催化剂（Cu-CCN）在不存在任何助催化剂或牺牲剂的情况下，表现出高度选择性和高效的光催化还原CO性能。单铜原子的引入可作为CO吸附位点，从而提高了Cu-CCN样品对CO的吸附能力。理论计算结果表明，在Cu-CCN样品上将CO还原为CH是一个熵增过程，而将CO还原为CO是一个熵减过程。结果，Cu-CCN样品表现出增强的光催化CO还原性能，对CO的选择性光催化转化接近100%。基于傅里叶变换红外光谱、X射线吸收光谱和密度泛函理论计算，提出了Cu-CCN样品上光催化CO还原的机理。这项工作为深入理解用于增强反应物活性位点的光催化剂设计提供了依据。
