Swapping CO2 electro-reduction active sites on a nickel-based hybrid formed on a “guilty” covalent triazine framework

A homogeneous and almost monodisperse Ni/CTFph composite of ultrasmall Ni NPs (similar to 2.2 nm) has been prepared by Metal Vapor Synthesis (MVS) and deposited on a highly porous and high specific surface area covalent triazine network. Metal doping was deliberately carried out on a metal-free system exhibiting superior CO2RR selectivity towards the challenging CO2-to-HCOOH electroreduction. Electrochemical studies aimed at shedding light on the CO2RR performance of the ultimate composite have allowed speculation on the synergistic or exclusive action of the two potentially active phases (N-doped C-network vs. Ni NPs). In contrast to the generally exclusive CO2-to-CO reduction mechanism described for the state-of-the-art Ni NP-based CO2RR electrocatalysts, Ni/CTFph has unveiled the unprecedented ability of Ni NPs to promote the alternative and more challenging 2e- CO2-to-HCOOH reduction pathway, even at moderately reducing potentials (-0.3 V vs. RHE).