Details

Autor(en) / Beteiligte

• Zhang, Xiaopeng
• Han, Xiangkai
• Wei, Yuying
• Wang, Xinxin
• Zhang, Ning
• Bao, Junjiang
• He, Gaohong

Titel

Single-atom Co-N-C catalyst for efficient Hg0 oxidation at low temperature

Ist Teil von

• Chemical engineering journal (Lausanne, Switzerland : 1996), 2022-01, Vol.428, p.132660, Article 132660

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2022

Quelle

Access via ScienceDirect (Elsevier)

Beschreibungen/Notizen

• [Display omitted] •Sigle-atom Co catalysts were successfully synthesized by a pyrolysis treatment.•Sigle Co atoms mainly coordinate with N and stay in CoN2.•CoN2 has a much higher oxygen adsorption energy compared to Co3O4.•The Hg0 oxidation activity of Co2.5-SAs@NC is about 100% even at 60 °C. Oxidation of Hg0 to Hg2+ is considered to be a promising method to remove Hg0 from flue gas. Chemisorbed oxygen on catalyst surface is the main active site during Hg0 oxidation process. Thus, how to efficiently activate gaseous oxygen forming more chemisorbed oxygen is a big challenge in this field. Inspired by this, metal Co based catalysts with an aggregation state of single Co atoms were prepared by pyrolysis of the redesigned bimetallic Zn/Co metal–organic frameworks precursor. SEM, TEM, HR-TEM and XRD results show that the catalysts have a high Co dispersion degree with lower Co doping content. HAADF-STEM has confirmed that Co2.5-SAs@NC (NC stands for nitrogen-doped carbon) has the aggregation state of single Co atoms. EXAFS results show that single Co atoms mainly coordinate with N and stay in Co-N2. Furthermore, DFT results determine that the adsorption energy of O2 on Co-N2 is much higher than that on the surface of traditional metal oxide catalyst Co3O4. It means single Co atoms have a better ability of transforming gaseous oxygen into chemisorbed oxygen. Thanks to the highly coordinated unsaturated state of single Co atoms and the better ability of transforming gaseous oxygen into chemisorbed oxygen, Co2.5-SAs@NC gains an excellent Hg0 oxidation efficiency of near 100% at high GHSV of 180, 000 h−1 even at a low temperature of 60 °C. With these advantages, Co2.5-SAs@NC appears to be a promising catalyst for Hg0 oxidation from flue gas.