室内甲醛污染已成为影响人类生命健康的重要问题之一。以氧气为氧化剂的催化氧化甲醛技术以其条件温和、无毒副产物等优势而受到广泛关注, 但是开发经济高效的催化材料仍然面临巨大的挑战。本工作通过一步水热法制备了α-Ni(OH)₂, 并研究了其催化氧化甲醛机理。测试结果表明, 以水为溶剂、硝酸镍为镍源制备的α-Ni(OH)₂在室温下催化氧化甲醛效率最高, 达到71.2%。原位红外和理论计算分析发现, 由于α-Ni(OH)₂表面丰富的羟基官能团, 吸附的甲醛与α-Ni(OH)₂表面羟基之间存在强烈的相互作用, 增强了对甲醛的活化, 在无氧气条件下实现了甲醛氧化。另一方面, 不同条件处理的α-Ni(OH)₂的XPS分析证实了催化氧化甲醛的活性位点为Ni³⁺, 且氧气可加速Ni³⁺活性位点的回复。α-Ni(OH)₂表面羟基协同活性位点Ni³⁺促进了甲醛的催化氧化, 这与传统氧气解离为速控步的甲醛氧化反应路径明显不同。本研究提出了表面羟基协同活性位点促进甲醛氧化的反应机理, 为催化氧化甲醛技术的实际应用提供了理论基础。

Indoor formaldehyde (HCHO) pollution has become one of the major issues affecting human health. Catalytic formaldehyde oxidation technology employing oxygen as oxidant has received extensive attention owing to its mild conditions and nontoxic byproducts, but developing affordable and effective catalysts remains a significant hurdle. In this work, α-Ni(OH)₂ was prepared through one-step hydrothermal method and its catalytic formaldehyde oxidation mechanism was investigated. The greatest catalytic formaldehyde elimination rate of 71.2% was demonstrated by α-Ni(OH)₂ at room temperature, which was made with water as the solvent and nickel nitrate as the nickel source. In situ DRIFTS and theoretical calculations revealed that, due to abundant hydroxyl functional groups on the surface of α-Ni(OH)₂, there was strong interaction between adsorbed formaldehyde and hydroxyl group on the surface of α-Ni(OH)₂, which promoted formaldehyde activation and achieved oxidation of formaldehyde without oxygen. On the other hand, the XPS spectra of α-Ni(OH)₂ treated under different conditions confirmed that the active sites of catalytic formaldehyde oxidation were Ni³⁺, and oxygen accelerated the recovery of Ni³⁺ active sites. The surface hydroxyl group of α-Ni(OH)₂ cooperated with the Ni³⁺ active sites achieved excellent catalytic efficiency of formaldehyde oxidation, which was obviously different from the traditional formaldehyde oxidation path with oxygen dissociation as the speed control step. Our work presents a new formaldehyde oxidation pathway controlled by synergy of surface hydroxyl and active sites, and offers a theoretical foundation for the actual use of catalytic formaldehyde oxidation.