The strongest result in this laboratory comparison was a molecular one: NiPc-OTh, a nickel phthalocyanine hybrid with a thiophene anchor, showed the strongest measured binding to copper oxide among the three molecules tested. CoPc-OTh came next, while NiPc showed the weakest binding evidence. The result gives researchers a concrete structure-activity clue for designing copper-based electrochemical catalysts, but the comparisons do not prove that the anchor alone caused any later difference in performance.
The underlying support was Cu2O in the form of nanocubes around 70 nanometres long. The hybrid set included NiPc@Cu2O, NiPc-OTh@Cu2O and CoPc-OTh@Cu2O, attached without changing the nano-cubic morphology. The reported comparison therefore kept the copper-oxide shape constant while the molecular partner varied.
A clearer signal in the binding tests
One test tracked how much the molecules' ultraviolet-visible absorption weakened after adsorption onto Cu2O. The attenuation was approximately 95% for NiPc-OTh, 65% for CoPc-OTh and 50% for NiPc. In ordinary terms, the biggest optical change occurred for NiPc-OTh. The order matched the study's binding ranking.
Computer modeling supplied a second line of evidence. The models gave negative adsorption-energy values for the molecules on Cu2O. They also placed two copper-sulfur bonds in the NiPc-OTh model, at 2.71 and 2.22 angstroms, while the CoPc-OTh model had one copper-sulfur bond at 2.34 angstroms. Together, the absorption and calculation results pointed to the strongest Cu2O interaction for NiPc-OTh within the tested set.
The activity gap appeared on another support
Binding was not the only comparison. On carbon nanotubes, the study examined NiPc-OTh@CNT, CoPc-OTh@CNT and NiPc@CNT for CO production. Both thiophene-anchored systems exceeded 90% CO Faradaic efficiency at potentials more negative than minus 0.65 volts, whereas NiPc@CNT needed minus 0.82 volts to pass the same threshold. CO Faradaic efficiency is the share of measured electrochemical output assigned to CO.
Current density gave a more detailed comparison. CoPc-OTh@CNT reached a CO partial current density of 31.8 milliamps per square centimetre at minus 0.77 volts. NiPc-OTh@CNT reached 25.8 milliamps per square centimetre at minus 0.80 volts, while NiPc@CNT reached 13.0 at minus 0.86 volts. Partial current density is the part of the electrical current associated with a product, adjusted for electrode area.
The reported measurements were taken at different potentials, so the current-density values are not a single same-condition contest. Even so, each thiophene-anchored system had a higher reported CO partial current than NiPc@CNT in the listed comparison. The broad contrast between the anchored and unanchored nickel systems appeared in both the selectivity and current measurements.
How the measurements were made
The molecular hybrids were made by a conventional cyclotetramerization route, purified by column chromatography and characterized with ultraviolet-visible spectroscopy and high-resolution mass spectrometry. For the Cu2O tests, the gas-tight H-cell used catalyst-coated carbon-fiber paper, an Ag/AgCl reference electrode and a platinum counter electrode in CO2-saturated KHCO3 electrolyte. Potentials were reported against the reversible hydrogen electrode with iR compensation.
The flow-cell work used PTFE-treated carbon-paper gas-diffusion electrodes with a continuous CO2 supply and KOH, together with platinum and Ag/AgCl counter and reference electrodes. Gas products were measured by gas chromatography with thermal-conductivity and flame-ionization detectors. Liquid products were measured by proton nuclear magnetic resonance, using DMSO as an internal standard; detailed analytical procedures were provided in the supplementary material.
What the result does not settle
No replicate count or uncertainty interval was reported for either the binding comparisons or the carbon-nanotube activity results. That means the size and repeatability of the differences cannot be judged from the reported summary alone.
The evidence supports an association between molecular design, surface binding and measured CO behavior in the tested systems. It does not establish that the thiophene anchor alone caused the difference, nor that the same performance order would hold with other supports or electrochemical conditions. For now, the work is best read as a design lead that still needs independently repeated measurements under clearly matched conditions.
Paper data and sources
Original title: Unveiling Structure‐Activity Relationship With Structurally Defined and Stabilized Cu‐Based Molecular Hybrid Electrocatalysts in CO2 Electroreduction
Authors: Wu J, Luo Z, Guo R et al.
Journal/Repository: Exploration (Beijing, China)
Status: Peer-reviewed
First online: 2026-10-13
DOI: Not available
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