Electrocatalytic CO 2 Reduction over Cu 3 P Nanoparticles Generated via a Molecular Precursor Route.

The design of nanoparticles (NPs) with tailored morphologies and finely tuned electronic and physical properties has become a key strategy for controlling selectivity and improving conversion efficiency in a variety of important electrocatalytic transformations. Transition metal phosphide NPs, in particular, have emerged as a versatile class of catalytic materials due to their multifunctional active sites and composition- and phase-dependent properties. Access to targeted transition metal phosphide NPs with controlled features is necessary to tune the catalytic activity. To this end, we have established a solution-synthesis route utilizing a molecular precursor containing M-P bonds to generate solid metal phosphide NPs with controlled stoichiometry and morphology. We expand here the application of molecular precursors in metal phosphide NP synthesis to include the preparation of phase-pure Cu 3 P NPs from the thermal decomposition of [Cu(H)(PPh 3 )] 6 . The mechanism of [Cu(H)(PPh 3 )] 6 decomposition and subsequent formation of Cu 3 P was investigated through modification of the reaction parameters. Identification and optimization of the critical reaction parameters (i.e., time, temperature, and oleylamine concentration) enabled the synthesis of phase-pure 9-11 nm Cu 3 P NPs. To probe the multifunctionality of this materials system, Cu 3 P NPs were investigated as an electrocatalyst for CO 2 reduction. At low overpotential (-0.30 V versus RHE) in 0.1 M KHCO 3 electrolyte, Cu 3 P-modified carbon paper electrodes produced formate (HCOO-) at a maximum Faradaic efficiency of 8%.