Intrinsic Defect-Rich Graphene Coupled Cobalt Phthalocyanine for Robust Electrochemical Reduction of Carbon Dioxide

Abstract

Carbon-based matrix is known to exert a profound influence on the stability and activity of a supported molecular catalyst for electrochemical CO2 reduction reaction (eCO2RR), while regulating the interfacial π–π interaction by designing functional species on the carbon matrix has seldom been explored. Herein, promoted π electron transfer between a graphene substrate and cobalt phthalocyanine (CoPc) is achieved by introducing abundant intrinsic defects into graphene (DrGO), which not only generates more electrochemically active Co sites and leads to a positive shift of the Co2+/Co+ reduction potential but also enhances the CO2 chemical adsorption. Consequently, as compared to the defect-free counterpart rGO-CoPc, DrGO-CoPc could yield CO with a Faradaic efficiency (FECO) higher than 85% in a wide potential range from −0.53 to −0.88 V, and the largest FECO and partial CO current density (J CO) achieve 90.2% and 73.9 mA cm–2, respectively. More importantly, both FECO and J CO can be dramatically improved when conducting eCO2RR in an ionic liquid-based electrolyte, for which FECO is higher than 90.0% in a wide potential range of 600 mV, with the peak J CO of up to 113.6 mA cm–2 in an H-type cell. The excellent eCO2RR performance of DrGO-CoPc rates itself as one of the best immobilized molecular catalysts.

Heterogenised Molecular Catalysts for Sustainable Electrochemical CO2 Reduction

“…The electrode reaches 100 % FE for CO at a potential applied of −0.53 V vs. RHE. In terms of current density in the H‐shaped cell, there is also an excellent material that reaches 30 mA cm −2 at −0.8 V vs. RHE in which a Co phthalocyanine is immobilised on defect‐rich graphene oxide [75] …”

“…In addition to doping and functionalisation of the carbon matrix, Liang et al [75] studied the influence of defects in the graphene substrate. Cobalt phthalocyanine was used again as a molecular complex and immobilised on reduced graphene oxide (rGO).…”

Electrocatalytic CO2Reduction: from Discrete Molecular Catalysts to Their Integrated Catalytic Materials

“…Upon a catalyst molecule immobilized onto a support or electrode, the interactions of support‐molecular‐catalyst are created and play a profound role in catalysis by: i) changing the electronic structure of metal center and even altering its redox potential/behavior; [77] ii) altering reaction pathway [9a] and even product distributions; [37a,78] iii) determining the efficiency of electron transfer between catalyst and support and the stabilization of the integrated material; [9a,37g] iv) shaping the reaction microenvironment (outer coordination sphere of catalyst) [79] . The loading and dispersion of catalysts also have great influence on ECR performance [37a] .…”

Influence of Carbon Support on the Pyrolysis of Cobalt Phthalocyanine for the Efficient Electroreduction of CO2

“…Notably, the addition of tert -butyl and cationic trimethyl ammonium (− + NMe 3 ) groups on the external benzene ring of CoPC, followed by adsorption onto CNT and incorporation as a heterogeneous catalyst into a flow cell electrolyzer, yielded outstanding CO 2 ERR properties for the selective formation of CO (>95%) at very high current densities ( J CO > 165 mA cm –2 ). , Modifying the supports is also a common way to enhance the CO production properties of CoPC-based systems. Some noteworthy examples include deposition onto defect-enriched graphene and nitrogen-doped hollow carbon spheres . A recently discovered method of achieving catalytic enhancement involves encapsulating CoPC into polyvinylpyridine polymers through axial coordination of the polymer’s side chain pyridine rings to the cobalt center .…”

“…21,22 Modifying the supports is also a common way to enhance the CO production properties of CoPC-based systems. Some noteworthy examples include deposition onto defect-enriched graphene 23 and nitrogen-doped hollow carbon spheres. 24 A recently discovered method of achieving catalytic enhancement involves encapsulating CoPC into polyvinylpyridine polymers through axial coordination of the polymer's side chain pyridine rings to the cobalt center.…”