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 (~ 2.2 nm) has been prepared by Metal Vapor Synthesis (MVS) 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 - as such - superior CO2RR selectivity towards the challenging CO2-to-HCOOH electroreduction. Electrochemical studies aimed at shedding light on the CO2RR performance of the ultimate composite, has allowed to speculate on the synergistic or exclusive action of the two potentially active phases (N-doped C-network vs. Ni NPs). At odds with a generally exclusive CO2-to-CO reduction mechanism described for Ni NPs-based CO2RR electrocatalysts of the state-of-the-art, Ni/CTFph has unveiled the unprecedented aptitude of Ni NPs to promote the alternative and more challenging 2e- CO2-to-HCOOH reduction path, already under moderately reducing potentials (-0.3 V vs. RHE).