青色顔料の改良でCO₂からCOへの変換性能を従来比で約4倍に向上～温暖化ガスを有効な化学原料に変える技術の社会実装へ～

2025-10-15 東北大学

東北大学材料科学高等研究所は、青色顔料の一種コバルトテトラアザフタロシアニン（CoTAP）を用いて、CO₂を一酸化炭素（CO）に高効率変換できる触媒を開発した。燃料電池や金属空気電池でも注目される安価な物質で、従来のコバルトフタロシアニン（CoPc）に比べ約4倍の質量活性と98％超の変換効率を達成。触媒中のピリジン性窒素が電子移動を促進することが高活性化の要因とされた。CO₂資源化技術の産業応用や温暖化ガス削減への寄与が期待される。成果は『Small』誌に掲載。

図1. 従来のCoPcを用いた検討(1)(2)とCoTAPを用いた本研究(3)。

＜関連情報＞

ピリジン-Nを組み込んだコバルトフタロシアニンを介したアンペアレベルのCO電気合成 Ampere-Level Electrosynthesis of CO via Well-Defined Pyridinic-N Incorporated Cobalt Phthalocyanine

Tengyi Liu, Xiaofan Hou, Di Zhang, Yutaro Hirai, Kosuke Ishibashi, Yasutaka Matsuo, Junya Yoshida, Shimpei Ono, Hao Li, Hiroshi Yabu
Small Published: 30 September 2025
DOI:https://doi.org/10.1002/smll.202507824

Abstract

High-rate CO electrosynthesis from CO₂ is vital for efficient CO₂-CO-C₂₊ tandem conversion. Cobalt phthalocyanine (CoPc), featuring a Co-N₄ site naturally favorable for CO production, suffers from low conductivity. Herein, a molecular engineering strategy is reported to construct cobalt tetra-aza-phthalocyanine (CoTAP) by incorporating four pyridinic-N atoms at the β-positions of the CoPc macrocyclic backbone, effectively enhancing both conductivity and intrinsic activity. The resulting CoTAP electrode achieves ≈100% CO selectivity at an ultralow onset overpotential of 140 mV (−0.25 V vs. RHE), significantly outperforming pristine CoPc (−0.57 V vs. RHE). Furthermore, it also delivers a record-high CO current density of −1084 mA cm⁻², an exceptional mass activity of 24,636.4 A g⁻¹, and an ultrahigh turnover frequency of 73.4 s⁻¹, with excellent stability for 112 h at −150 mA cm⁻², surpassing all reported Pc-based catalysts. Systematic analysis shows that pyridinic-N incorporation alters the electronic environment around Co centers and reduces resistance to only 3.8% of CoPc. Theoretical calculations further confirm more favorable adsorption energies for key intermediates (^*COOH and ^*CO), underpinning the enhanced intrinsic activity. Collectively, these advancements maximize site-specific reaction kinetics in CoTAP. This work presents a molecular-level strategy to simultaneously boost conductivity and intrinsic activity for advanced CO₂ electroreduction.