Efficient amino-acid-based reactive capture of CO₂ via nickel molecular catalyst.

Abstract

Reactive capture integrates CO₂ capture and electrochemical conversion into CO - a key building block in the synthesis of industrial chemicals and fuels - avoiding costly regeneration steps and improving efficiency. Amino acid salt solutions, which offer rapid CO₂ capture, facile CO₂ release, O₂ tolerance, and low toxicity, are promising sorbents for reactive capture. However, we find that amino acids can adsorb to common CO-producing catalysts, covering the active sites and deactivating the catalyst, and that they bind less to nickel phthalocyanine (NiPc). Still, when tested for reactive capture systems - where CO₂ supply is inherently limited - NiPc's performance is constrained by its weak CO₂ adsorption and activation. Here we develop a nickel molecular catalyst supported on carbon nanotubes with a conjugated NiPc framework that resists amino acid adsorption and a coordinatively unsaturated Ni-N₃ structure that promotes CO₂ adsorption and enhances CO selectivity. As a result, we achieve 94% CO Faradaic efficiency at 100 mA cm^-2 with an energy efficiency of 42% and an energy cost of 25 GJ t_CO^-1.