Tuning chemical bonding of MnO2 through transition-metal doping for enhanced CO oxidation

• Published in: Journal of catalysis 2016-09, Vol.341, p.82-90
• Main Authors: Gao, Jiajian, Jia, Chunmiao, Zhang, Liping, Wang, Hongming, Yang, Yanhui, Hung, Sung-Fu, Hsu, Ying-Ya, Liu, Bin
• Format: Article
• Language: English
• Subjects: Catalysis; Catalysts; Catalytic CO oxidation; Catalytic oxidation; Chemical synthesis; DFT calculation; Doping; MnO2 nanowires; Nanowires
• ISSN: 0021-9517; 1090-2694
• DOI: 10.1016/j.jcat.2016.06.009

[Display omitted] •Fe-, Co-, Ni-, and Cu-doped α-MnO2 nanowires were synthesized by a one-step hydrothermal method.•All doped MnO2 nanowires exhibited much enhanced CO oxidation activity.•The Cu-doped MnO2 nanowires had a maximum TOF of 9.1×10−3s−1 at 70°C.•Cu-doped MnO2 could maintain 50h without obvious deactivation with 2% water moisture.•Cu doping makes the formation of oxygen vacancies easier in MnO2. Replacing a small fraction of cations in a host metal oxide with a different cation (also known as doping) provides a useful strategy for improving the catalytic activity. Here, we report transition metal (Fe, Co, Ni, and Cu)-doped α-MnO2 nanowires synthesized by a one-step hydrothermal method as CO oxidation catalysts. The as-prepared catalysts displayed morphology, crystal structure, and specific surface area similar to those of the pure MnO2 nanowires. A catalytic activity test showed that all doped MnO2 nanowires exhibited much enhanced CO oxidation activity, with the Cu-doped ones being the most active (TOF of 9.1×10−3s−1 at 70°C). The Cu-doped MnO2 nanowires showed nearly 100% conversion of CO at 100°C at an hourly gas space velocity of 36,000mLg−1h−1, which could last for 50h without obvious deactivation even in the presence of 2% water vapor. Density functional theory calculations suggested that Cu doping could make the formation of oxygen vacancies in MnO2, which is the rate-determining step for CO oxidation reaction, easier than for Fe-, Co-, and Ni-doped and pristine MnO2. Our work demonstrates a facile and promising strategy for improving the catalytic activity for oxide-based catalysts, which should be applicable for a variety of different chemical reactions.