High‐Rate and Selective Conversion of Low‐Concentration Carbon Dioxide to Carbon Monoxide Using a Carbon Nanotube‐Supported Molecular Electrocatalyst

Why It Matters

The breakthrough enables high‑rate, selective CO production from dilute CO2 sources, expanding the economic viability of renewable‑powered carbon capture and utilization.

Key Takeaways

• Molecularly dispersed CoPc on MWCNT boosts active site accessibility
• CuPc addition prevents CoPc aggregation, enhancing CO2 adsorption
• 65.7% CO selectivity achieved at 20% CO2, 0.625 A
• Energy efficiency reaches 54.8% under ampere-level operation
• Stable >72 h, FECO >80% in simulated biogas

Pulse Analysis

Electrochemical CO2 reduction (e‑CO2RR) has emerged as a promising pathway to convert greenhouse gases into value‑added chemicals, yet most catalysts struggle with low‑concentration streams typical of industrial flue gases. Conventional metal surfaces often require high CO2 partial pressures to achieve reasonable turnover, limiting their deployment in biogas or post‑combustion contexts. Molecular electrocatalysts, particularly phthalocyanine complexes, offer tunable electronic structures and strong CO2 affinity, but their practical use has been hampered by aggregation and poor conductivity when deposited on bulk supports.

The MWCNT|CuPc‑CoPc architecture addresses these hurdles by anchoring CoPc molecules on a conductive carbon nanotube scaffold while interspersing CuPc to act as a steric and electronic moderator. Density‑functional theory calculations reveal that CuPc demetallization during operation creates H2Pc sites that further enhance CO2 adsorption, effectively lowering the activation barrier for CO formation. This synergistic design translates into a single‑pass CO yield of 65.7 % and an energy efficiency near 55 % at an industrially relevant current density, outperforming many metal‑based systems under identical low‑CO2 conditions.

From a commercial perspective, the demonstrated durability—maintaining >80 % Faradaic efficiency for over three days in a 40 % CO2/60 % CH4 mixture—signals readiness for scale‑up in renewable‑energy‑driven carbon capture facilities. The ability to operate efficiently at ampere‑level currents reduces capital costs for power electronics, while the modular GDE format facilitates integration with existing gas‑handling infrastructure. Future work will likely focus on further optimizing metal‑phthalocyanine ratios, extending catalyst lifetimes, and coupling the process with downstream CO utilization routes such as Fischer‑Tropsch synthesis, thereby closing the loop on sustainable carbon recycling.