Microstructure Design Strategy for Molecularly Dispersed Cobalt Phthalocyanine and Efficient Mass Transport in CO₂ Electroreduction

Abstract

Cobalt phthalocyanine (CoPc) has attracted particular interest owing to its excellent activity during the electrochemical CO2 conversion to CO. However, the efficient utilization of CoPc at industrially relevant current densities is still a challenge owing to its nonconductive property, agglomeration, and unfavorable conductive substrate design. Here, a microstructure design strategy for dispersing CoPc molecules on a carbon substrate for efficient CO2 transport during CO2 electrolysis is proposed and demonstrated. The highly dispersed CoPc is loaded on a macroporous hollow nanocarbon sheet to act as the catalyst (CoPc/CS). The unique interconnected and macroporous structure of the carbon sheet forms a large specific surface area to anchor CoPc with high dispersion and simultaneously boosts the mass transport of reactants in the catalyst layer, significantly improving the electrochemical performance. By employing a zero‐gap flow cell, the designed catalyst can mediate CO2 to CO with a high full‐cell energy efficiency of 57% at 200 mA cm−2.

A universal route to graft highly dispersed cobalt phthalocyanine on porous carbon for efficient CO2 electroreduction

“…2e, all catalysts presented typical type II isotherms with type-H3 hysteresis loops, reflecting the existence of mesopores in the catalysts. 26 Besides, a steep N 2 uptake at high relative pressures was also observed, indicating that macropores also formed in these catalysts. The specific surface area of CoPc/PC-800 was 339.7 m 2 g −1 , which were significantly larger than 90.8 m 2 g −1 for CoPc/PC-700, 74.1 m 2 g −1 for CoPc/PC-900 and 6.6 m 2 g −1 for CoPc/C-800.…”

“…However, most carbon supports mainly contain micropores (<2 nm) and mesopores (2–50 nm). In view of the average free path of CO 2 molecules being 84 nm, 26 the diffusion efficiency and local concentration of CO 2 in the catalytic layer would be reduced, resulting in a decreased catalytic performance. Therefore, to boost the dispersion of CoPc and the mass transportation during the CO 2 RR simultaneously, rational structural design of the carbon substrate is highly desirable for more efficient catalysis.…”

Ni Single Atoms Embedded in Graphene Nanoribbon Sieves for High‐Performance CO2 Reduction to CO

“…To describe the gases diffusion ability in complex porous electrodes, this work adopts a method by recording the ORR current at varied O 2 partial pressure in N 2 feed. [ 52,53 ] As illustrated in the Figure 6b, the current density of ORR (j ORR ) starts to decline at low oxygen partial pressure >0.4 bar (kinetically limited zone), the j ORR of three catalyst shows little difference. At low oxygen partial pressure (mass transfer limited zone), the gases diffusion starts to dominate the current density.…”