Metal-Coordinated Phthalocyanines as Platform Molecules for Understanding Isolated Metal Sites in the Electrochemical Reduction of CO₂

Abstract

Single-atom catalysts (SACs) of non-precious transition metals (TMs) often show unique electrochemical performance, including the electrochemical carbon dioxide reduction reaction (CO 2 RR). However, the inhomogeneity in their structures makes it difficult to directly compare SACs of different TM for their CO 2 RR activity, selectivity, and reaction mechanisms. In this study, the comparison of isolated TMs (Fe, Co, Ni, Cu, and Zn) is systematically investigated using a series of crystalline molecular catalysts, namely TM-coordinated phthalocyanines (TM-Pcs), to directly compare the intrinsic role of the TMs with identical local coordination environments on the CO 2 RR performance. The combined experimental measurements, in situ characterization, and density functional theory calculations of TM-Pc catalysts reveal a TMdependent CO 2 RR activity and selectivity, with the free energy difference of ΔG(*HOCO) − ΔG(*CO) being identified as a descriptor for predicting the CO 2 RR performance.

Probing the Synergistic Effects of Mg2+ on CO2 Reduction Reaction on CoPc by In Situ Electrochemical Scanning Tunneling Microscopy

“…80% CO Faradaic efficiency (FE CO ) in a wide potential range in Mg 2+ -containing electrolytes, and other reduced forms of CO 2 are not detected (Figure S1a). The selectivity results of the CoPc-catalyzed CO 2 RR are in agreement with previous reports . The electrochemical measurement shows the high stability of the CoPc-modified electrode during CO 2 RR.…”

“…The selectivity results of the CoPc-catalyzed CO 2 RR are in agreement with previous reports. 33 The electrochemical measurement shows the high stability of the CoPc-modified electrode during CO 2 RR. Apparent decay in catalytic activity is not observed after 6 h of electrocatalysis (Figure S1b), which is in accord with the previous reports.…”

Rational Design of Metal–Organic Frameworks for Electroreduction of CO2 to Hydrocarbons and Carbon Oxygenates

“…Conductive ligand design has an essential impact on the intrinsic conductivity of MOFs. The organic ligands with large π-conjugated structures can effectively manipulate the electron transfer ability of MOFs. , Mirica et al developed a series of 2D, π-conjugated phthalocyanine MOFs with different metal ions . Thereinto, CoPc-Cu-O exhibits a conductivity of 2.12 S m –1 and a current density of 9.5 mA cm –2 with an FE­(CO) of 79% in 0.1 M KHCO 3 solution.…”

Impaired conjugation boosts CO2 electroreduction by Ni(ii) macrocyclic catalysts immobilized on carbon nanotubes

“…6–8 Furthermore, compared to the conventional single-atom catalysts, 9 the immobilized molecular catalysts are more advantageous in retaining their modulable structures and easy realization of mechanistic research. 5,10…”

“…[6][7][8] Furthermore, compared to the conventional singleatom catalysts, 9 the immobilized molecular catalysts are more advantageous in retaining their modulable structures and easy realization of mechanistic research. 5,10 Based on the above advantages, extensive research studies have been carried out on the molecular electrodes, aiming at improvements in the catalytic activity through ligand design, 11,12 as well as the optimization of supports 13,14 and molecule-support interactions. 15,16 Among them, extending the conjugation of ligands has been widely reported as an effective strategy to improve catalytic performances.…”