Prof. Yongye Liang’s research group has developed highly selective and active electrocatalysts for carbon dioxide reduction. This work has been recently published in the journal “Nature Communications” entitled “Highly Selective and Active CO2 Reduction Electrocatalysts Based on Cobalt Phthalocyanine/Carbon Nanotube Hybrid Structures”.
The Global carbon cycle plays a key role in our planet’s sustainability. However, human activities in the past centuries have significantly increased the amount of CO2 in the atmosphere. The electrocatalytic reduction of CO2 to useful carbon based products is a promising solution to this problem. It can work under ambient condition in water and be coupled with renewable energy sources like solar energy. Currently, electroreduction of CO2 suffers from high overpotential of the operation and low selectivity of the desired product. Cost-effective electrocatalysts with high activity, selectivity and good stability are highly desirable to make the CO2 electroreduction process industrially viable.
Liang and his coworkers reported a cobalt phthalocyanine (CoPc) based high-performance CO2 reduction electrocatalyst material developed with a combined nanoscale and molecular approach. On the nanoscale, CoPc molecules are uniformly anchored on carbon nanotube (CNT) walls with strong pi-pi interaction between them to form the CoPc/CNT hybrid, affording substantially increased current density and improved catalytic selectivity and stability compared to CoPc for electroreduction of CO2 to CO(an important industrial gas that has many applications in bulk chemicals manufacturing). The CoPc/CNT hybrid catalyst shows a high and stable current density of around 10 mA cm-2 with a FE of over 90% for CO2 reduction to CO at an overpotential of 0.52 V in 0.1 M KHCO3 aqueous solution for over 10 hours. On the molecular level, the catalytic performance is further upgraded by introducing cyano groups to the CoPc molecules (CoPc-CN). The resulting CoPc-CN/CNT hybrid material converts CO2 to CO selectively with Faradaic efficiencies over 95% in a wide potential range and demonstrates extraordinary catalytic activity with a current density of 15.0 mAcm-2 and a turnover frequency of 4.1 s-1 at the overpotential of 0.52 V in 0.1 M KHCO3 aqueous solution. The hybrid catalysts deliver high geometrical catalytic current densities comparable to the best heterogeneous catalysts while maintaining good per-site activity comparable to the best molecular systems for CO2 electroreduction to CO. The study reveals that these molecule/CNT hybrid materials represent an attractive class of electrocatalysts for converting CO2 emissions to sustainable fuels.
Fig 1. a) TEM image of the CoPc/CNT (6%) hybrid overlaid with schematic representation of the CoPc/CNT hybrid and Raman spectra of pure CoPc, CoPc/CNT (6%) hybrid and pure CNT；b) Faradaic efficiencies of CO2 reduction gas products for CoPc/CNT (2.5%) (red) and CoPc (blue) at various potentials in 0.1M KHCO3 aqueous solution；c) Chronoamperograms and d) Faradaic efficiencies of reduction products at various potentials for CoPc-CN/CNT（solid line）and CoPc-CNT（dotted line）in 0.1M KHCO3 aqueous solution.
Xing Zhang, Zishan Wu (Yale University), Xiao Zhang and Liewu Li are the first authors with equal contributions. Other coworkers include Yanyan Li, Xiaoxiao Li, Haomin Xu, Xiaolu Yu,Zisheng Zhang and Prof. Hailiang Wang (Yale University). This work was supported by “The Recruitment Program of Global Youth Experts of China”, Shenzhen fundamental research funding (JCYJ20160608140827794), Shenzhen Key Lab funding (ZDSYS201505291525382) and Peacock Plan (KQTD20140630160825828).
Paper link：http://www.nature.com/articles/ncomms14675
