Modulating the coordination environment and metal choice in carbon buckypapers supported metal phthalocyanines for enhanced electrocatalytic carbon dioxide reduction

• Carbon nanotubes buckypapers as electrocatalysts for the electrochemical reduction of carbon dioxide. • Metal nature and surface chemistry of the buckypapers play a pivotal role in the CO 2 RR efficiency and selectivity. • Syngas is the main product from CO2RR using FePc, CoPc and NiPc as electrocatalysts. • H 2 /CO ratios between 0.17 and 1.28 are obtained with good stability during electrolysis. In the search of versatile electrocatalysts for the electrochemical reduction of carbon dioxide (CO 2 RR), different transition metal phthalocyanines (MPc, where M=Fe, Co, Ni and Cu) have been immobilized by an easy and scalable wet impregnation on carbon nanotubes (CNTs) in the form of buckypaper (BP). Both the nature of the metal and the surface chemistry of the carbon support were found to play a pivotal role in determining their CO 2 RR efficiency and selectivity. We disclose here a potentiodynamic strategy for the controlled surface modification of BP with N- and P-containing polymeric species as a simple heterogenization strategy for molecular catalysts, enabling to easily tune their electrocatalytic performance. Syngas (mixture of H 2 and CO) was obtained as the main product from CO 2 RR using FePc, CoPc and NiPc as electrocatalysts on functionalized (BP f ) or non-modified BP. In contrast, CuPc was found to mainly catalyze the hydrogen evolution reaction (HER), with small amounts of formate as the only CO 2 RR product. It is possible to modulate the H 2 /CO ratio in the final product through the appropriate selection of the metal in MPc, the modification of the coordination environment by the controlled functionalization of the carbon support and the adjustment of the operating conditions. In particular, H 2 /CO ratios in a range between 0.17 and 1.28 have been obtained with good stability during electrolysis. Among all the MPc studied, CoPc surfaced as the most promising candidate for the reduction of CO 2 to CO and H 2 production, a finding substantiated by computational studies highlighting the positive impact of phosphate ligands on CoPc. This strategy outlines the starting line of a potential route toward the controlled generation of CO 2 RR-related products.