The electrocatalytic CO₂ reduction reaction (eCO₂RR) is a feasible project to alleviate environmental problems, optimize high value-added production and accelerate energy storage, which can be said to kill three birds with one stone. Crucially, how to design and construct efficient electrocatalysts under industrial-level operation has important strategic significance. 

The π-conjugated metallomacrocyclic molecules (e.g., phthalocyanines and porphyrins) heterogenized at the single-molecular level, namely single-molecular heterojunction (SMH) electrocatalysts, offer an ideal platform for eCO₂RR and reaction mechanism studies due to the definite coordination structures of metal centers, relatively uncomplicated synthetic procedures and flexible design assembling. Nevertheless, the selectivity and durability are needed to be further improved at the industrial-level current densities with low overpotentials. 

Prof. ZHU Qilong’s group from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences, reported an enzyme-inspired SMH ((NH_x)₁₆-NiPc/CNTs) as the anodic and cathodic electrocatalysts for efficiently producing CO and recycle sulfur via coupling selectively electrocatalytic eCO₂RR and S^2– oxidation with greatly reduced energy input at the simulated industrial level. 

The study was published in Advanced Materials on June 28. 

The as-prepared (NH_x)₁₆-NiPc/CNTs exhibited exceptional electrocatalytic performances for CO₂-to-CO, simultaneously possessing ~100% FE_CO, large current densities and excellent durability in a wide potential window.  

(NH_x)₁₆-NiPc/CNTs assembled into the gas diffusion electrode was implemented to evaluate industrial eCO₂RR performance in a flow cell, and the outstanding selectivity and durability can be maintained at commercializable current densities.  

Experiments results unraveled that the significantly improved performance is consistent with the unique amino-rich local micro-environments offering the significant chemisorption and proton ferry effect, which efficiently enrich CO₂ reactants and boost proton transfer to nickel active sites.  

By using (NH_x)₁₆-NiPc/CNTs as a novel bifunctional electrocatalyst in a two-electrode flow electrolyzer,  the researchers neatly integrated the highly active CO₂-to-CO conversion at the cathode with sulfion oxidation to recycle sulfur at the anode instead of uneconomical O₂ evolution, achieving the electrochemical pair-production of value-added feedstocks at both electrodes with higher production efficiency yet greatly reduced energy input. 

This study paves the new way in exploring molecular electrocatalysts and electrolysis systems with techno-economic feasibility. 

Illustration of the Research (Image by Prof. ZHU’s group) 

Contact:  

Prof. ZHU Qilong 

Fujian Institute of Research on the Structure of Matter 

Chinese Academy of Sciences 

Email: qlzhu@fjirsm.ac.cn