Metal-Free Polyphthalocyanine with Implanted Built-In Electric Field Enabling High-Efficiency CO₂ Electroreduction

Metal phthalocyanine (Pc)-based molecular catalysts are able to achieve an efficient carbon dioxide electroreduction reaction. Nonetheless, the further development of metal Pc is greatly limited by reserves and geographical distribution differentiation of metal strategic resources, such as Co and Ni. Herein, a metal-free polyphthalocyanine/carbon tube (PPc/CNT) electrocatalyst was activated by a double electron transfer strategy and creatively exhibited a performance comparable to that of metal Pc-based electrocatalysts. The electron-rich charge state of the PPc/CNT catalyst generated by the built-in electric field induced a unique CO2-dependent response, in which the adsorbed CO2 on its surface trapped the free electrons from PPc/CNT, accompanied by a switch from an electron-rich to an electron-deficient feature, thus restraining the hydrogen evolution reaction. The PPc/CNT with an electron-rich carbon site can still keep over 95% of the high CO Faradaic efficiency in a wide potential region of 600 mV, superior to that of reported Pc-based electrocatalysts. Theoretical studies revealed that the C site (adjacent to two N sites in pyrrolic N and C-N & boxH;C) in the catalyst featured low CO2 adsorption energy and enhanced CO2 activation capability compared with that of two N sites, being the intrinsically active center.