Scientists from Tohoku University, Hokkaido University, and AZUL Energy, Inc. have created a simplified method for turning carbon dioxide (CO2) into carbon monoxide (CO), a crucial building block for synthetic fuels. Thanks to their method's record-breaking efficiency, the time needed was reduced from 24 hours to just 15 minutes. The journal Advanced Science published this study.
Fabrication method of gas diffusion electrodes modified with metal phthalocyanine crystals, and the characteristics and performance when using cobalt phthalocyanine (CoPc) crystals. Image Credit: Hiroshi Yabu et al.
Imagine if one could transform harmful pollution into a valuable energy source. Investigating energy innovations that reduce pollution is essential in pursuing carbon neutrality.
CO2-to-CO conversion is currently a hot topic to address climate change, but the conventional techniques had major pitfalls that we wanted to address. The materials were expensive, unstable, had limited selectivity, and took a long time to prepare. It just would not be feasible to use them in an actual industrial setting.
Tengyi Liu, Study Corresponding Author, WPI-Advanced Institute for Materials Research, Tohoku University
The researchers chose different phthalocyanines (Pc) that are expected to enhance performance, including metal-free (H2Pc), iron (FePc), cobalt (CoPc), nickel (NiPc), and copper (CuPc) while keeping in mind industry standards.
These were sprayed onto gas diffusion electrodes to directly create crystalline layers of the phthalocyanines on the electrode surface. Ultimately, CoPc, a cheap pigment and metal complex, demonstrated the best efficiency in turning CO2 into CO.
This graffiti-style technique, which involves simply spraying the catalyst on a surface, lowers the usual processing time to just 15 minutes. Conventional methods required the laborious process of combining conductive carbon and binders, drying, and heat treating over a 24-hour period.
For 144 hours, the new system operated steadily at a current density of 150 mA/cm². The researchers verified that their catalyst outperformed all previously documented Pc-based catalysts using the DigCat Database, which is currently the largest experimental electrocatalysis database.
Not only is this the best Pc-based catalyst for producing CO to date, but it successfully exceeds the industrial standard thresholds for its reaction rate and stability. It is the first ever to make the cut.
Tengyi Liu, Study Corresponding Author, WPI-Advanced Institute for Materials Research, Tohoku University
The team used theoretical calculations and synchrotron radiation structural analysis at the NanoTerasu facility to explore the causes of this high performance. The findings implied that densely packed molecules produced by crystallization enabled effective electron transfer to the surface. These results demonstrate that direct crystallization successfully creates catalyst electrodes for CO₂ electroreduction based on metal complexes.
Together with the CO2 electrolysis technology, the gas diffusion electrode fabrication method created in this work presents a viable route for the highly efficient synthesis of carbon monoxide (CO), a crucial intermediate for synthetic fuels, from CO2 using inexpensive pigment-based catalysts.
By increasing energy efficiency and lowering CO2 utilization costs, this strategy tackles one of the main production bottlenecks for synthetic fuel.
It, therefore, has a lot of promise as a next-generation carbon dioxide capture and utilization (CCU) technology.
Journal Reference:
Liu, T., et al. (2025) Surface Charge Transfer Enhanced Cobalt‐Phthalocyanine Crystals for Efficient CO2‐to‐CO Electroreduction with Large Current Density Exceeding 1000 mA cm−2. Advanced Science. doi.org/10.1002/advs.202501459.