Alkali-modified copper manganite spinel for room temperature catalytic oxidation of formaldehyde in air

Abstract

Formaldehyde (FA) is present ubiquitously in indoor environment as a hazardous pollutant with carcinogenic risks. For the efficient mitigation of FA, catalytic oxidation is a recommendable option to simultaneously satisfy both material cost (e.g., avoiding noble metals) and low-energy requirement (under dark and at room temperature (RT)). From this perspective, a cost-effective alkali modified copper manganite spinel (CuMn2O4) catalyst has firstly been prepared and employed for FA oxidation. Specifically, alkali (1 mol L−1 potassium hydroxide)-modified CuMn2O4 (1-CuMn2O4) achieves 100% FA (50 ppm (gas hourly space velocity of 4777 h−1)) conversion (XFA) at RT. The steady-state reaction rate of 1-CuMn2O4 at 10% XFA is 8.18 × 10−2 mmol g−1 h−1. According to in situ diffuse reflectance infrared Fourier transform spectroscopy, FA molecules are oxidized into water and carbon dioxide through dioxymethylene and formate intermediates. Based on density functional theory simulation, the higher catalytic performance of 1-CuMn2O4 for FA oxidation is attributed to the combined effects of firmer attachment of FA molecules to 1-CuMn2O4 surface, lower energy cost of FA adsorption, and lower desorption energy for the final products from the substrate surface. The present work is expected to provide insights into high-performing non-noble metal catalysts for RT oxidative removal of FA from indoor air.

甲醛(FA)作为一种有致癌风险的有害污染物, 在室内环境中普遍存在. 为了高效去除甲醛, 催化氧化技术成为了一种既经济又节能的选择, 它不仅能降低材料成本(例如避免使用贵金属), 也能在无光和室温的条件下进行. 本文制备了一种成本效益高的碱改性锰酸铜尖晶石(CuMn2O4)催化剂, 并用于甲醛催化氧化反应中. 实验结果表明, 采用碱(1 mol L‒1 氢氧化钾)改性的CuMn2O4 (1-CuMn2O4)作为催化剂, 在室温条件下, 当甲醛浓度为50 ppm, 气体空速为 4777 h‒1 时, 甲醛转化率(XFA)达到100%; 此外, 在甲醛转化率为10%时, 其稳态反应速率达到了8.18 × 10‒2 mmol g‒1 h‒1 . 原 位漫反射红外傅立叶变换光谱结果表明, 在催化剂的作用下, 甲醛分子经过二氧亚甲基和甲酸酯中间体的转化, 最终被氧 化为水和二氧化碳. 进一步结合密度泛函理论模拟发现, 1-CuMn2O4具有较高的催化氧化甲醛性能, 可归因于甲醛分子更牢固地吸附在1-CuMn2O4表面, 甲醛吸附所需的能量较低, 以及最终产物从催化剂表面脱附所需的能量也较低的综合效应. 本研究为在无光和室温条件下, 高效去除空气中甲醛提供了新型高效、成本效益高且无需贵金属的催化剂, 从而为室内空气净化提供了新的科学见解.