| 研究実績の概要 |
The current fossil fuels are unsustainable and cause global warming. So, discovering alternative fuels is indispensable. CH3OH is currently proposed as one of the best new fuels. One promising approach for production of CH3OH is artificial photosynthesis system. In this system, water oxidation and CO2-to-CO conversion occur at anode and cathode, respectively based on electric power generation by a solar cell. Finally, CO is converted to a methanol fuel by the well-known Fischer-Tropsch method. A key factor for efficient solar-driven fuel production by artificial photosynthesis is developing efficient catalysts for CO2-to-CO conversion. Here we developed several cheap iron non-heme complexes, Fe(bpb) that showed high activity for CO2 reduction with 93% CO faradaic efficiency at a moderate overpotential η = 0.41 V in homogeneous CO2-saturated DMF solutions. One of these catalysts, Fe(bpc) was immobilized on a nitrogen-doped graphene (NG) electrode to achieve efficient and selective CO2-to-CO conversion in neutral aqueous NaHCO3 solutions (pH =7.3), generating 6 mA/cm2 current density with very high TOF values of 1120 s－1 at η = 0.47 V. These values are among the highest reported values achieved by molecular catalysts in aqueous solutions. Moreover, the Fe(bpc) and Ni(bpc) complexes are co-adsorbed on the NG electrode where their performance are much improved, generating 18 mA/cm2 current density, indicating the cooperative effect of the Fe and Ni centers in a similar way observed by FeNi enzyme called "Carbon Monoxide De-Hydrogenase”
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