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Many metal coordination compounds catalyze CO₂electroreduction to CO, but cobalt phthalocyanine hybridized with conductive carbon such as carbon nanotubes is currently the only one that can generate methanol. The underlying structure–reactivity correlation and reaction mechanism desperately demand elucidation. Here we report the first in situ X‐ray absorption spectroscopy characterization, combined with ex situ spectroscopic and electrocatalytic measurements, to study CoPc‐catalyzed CO₂reduction to methanol. Molecular dispersion of CoPc on CNT surfaces, as evidenced by the observed electronic interaction between the two, is crucial to fast electron transfer to the active sites and multi‐electron CO₂reduction. CO, the key intermediate in the CO₂‐to‐methanol pathway, is found to be labile on the active site, which necessitates a high local concentration in the microenvironment to compete with CO₂for active sites and promote methanol production. A comparison of the electrocatalytic performance of structurally related porphyrins indicates that the bridging aza‐N atoms of the Pc macrocycle are critical components of the CoPc active site that produces methanol. In situ X‐ray absorption spectroscopy identifies the active site as Co(I) and supports an increasingly non‐centrosymmetric Co coordination environment at negative applied potential, likely due to the formation of a Co−CO adduct during the catalysis.

 

Many metal coordination compounds catalyze CO₂electroreduction to CO, but cobalt phthalocyanine hybridized with conductive carbon such as carbon nanotubes is currently the only one that can generate methanol. The underlying structure–reactivity correlation and reaction mechanism desperately demand elucidation. Here we report the first in situ X‐ray absorption spectroscopy characterization, combined with ex situ spectroscopic and electrocatalytic measurements, to study CoPc‐catalyzed CO₂reduction to methanol. Molecular dispersion of CoPc on CNT surfaces, as evidenced by the observed electronic interaction between the two, is crucial to fast electron transfer to the active sites and multi‐electron CO₂reduction. CO, the key intermediate in the CO₂‐to‐methanol pathway, is found to be labile on the active site, which necessitates a high local concentration in the microenvironment to compete with CO₂for active sites and promote methanol production. A comparison of the electrocatalytic performance of structurally related porphyrins indicates that the bridging aza‐N atoms of the Pc macrocycle are critical components of the CoPc active site that produces methanol. In situ X‐ray absorption spectroscopy identifies the active site as Co(I) and supports an increasingly non‐centrosymmetric Co coordination environment at negative applied potential, likely due to the formation of a Co−CO adduct during the catalysis.

 

Multi-component materials are a new trend in catalyst development for electrochemical CO 2 reduction. Understanding and managing the chemical interactions within a complex catalyst structure may unlock new or improved reactivity, but is scientifically challenging. We report the first example of capping ligand-dependent metal–oxide interactions in Au/SnO 2 structures for electrocatalytic CO 2 reduction. Cetyltrimethylammonium bromide capping on the Au nanoparticles enables bifunctional CO 2 reduction where CO is produced at more positive potentials and HCOO − at more negative potentials. With citrate capping or no capping, the Au–SnO 2 interactions steer the selectivity toward H 2 evolution at all potentials. Using electrochemical CO oxidation as a probe reaction, we further confirm that the metal–oxide interactions are strongly influenced by the capping ligand.