News from Nanotechjapan

合成・材料

Development of Artificial Denitrification Catalyst by Mimicking Microbial Enzymes

 On March 29, 2018, Riken announced that the international research group including Biofunctional Catalyst Research Team at Riken, Shanghai Jiao Tong University, Korea Basic Science Institute, and the University of Tokyo succeeded in developing artificial denitrification catalyst by mimicking microbial enzymes to result in efficient reduction of nitrate and nitrite to dinitrogen under mild conditions. Details were published in Journal of the American Chemical Society*.

 Denitrification is a crucial process in waste water treatment against the pollution by nitrogen oxides coming from nitrogen fertilizer and domestic animal wastes for instance. Conventional biological denitrification processes require large equipment and they are not suitable for the treatment of waste water with highly concentrated nitrogen oxides. Although artificial catalysts are tried instead of enzyme, the process needs precious metal catalysts and strongly acidic conditions.

 The research group investigated denitrification process of microbial enzymes in detail and found that they have metallic elements such as iron (Fe), copper (Cu), and molybdenum (Mo) as an active center for selective reduction of nitrogen oxides under mild conditions. Especially, the enzyme having Mo in its active center showed the ability of reducing NO₃⁻. Then, the group synthesized a catalyst with MoS₄ structure by hydrothermal synthesis and tested the catalytic activity. 

 The selectivity of this oxo-molybdenum sulfide electrocatalyst toward nitrite reduction to dinitrogen exhibited a volcano-type pH dependence with a maximum at pH 5. The pH-dependent formation of the intermediate species identified using electron paramagnetic resonance (EPR) and Raman spectroscopy was in accord with a mathematical prediction. An efficiency of 13.5% was recorded for nitrite reduction to dinitrogen under neutral conditions. 

*Daoping He, Yamei Li, Hideshi Ooka, Yoo Kyung Go, Fangming Jin , Sun Hee Kim, and Ryuhei Nakamura, "Selective electrocatalytic reduction of nitrite to dinitrogen based on decoupled proton-electron transfer", Journal of the American Chemical Society, Vol. 140, No. 6, pp 2012-2015 (2018), DOI: 10.1021/jacs.7b12774; Publication Date (Web): January 29, 2018