Noble metal monolayer shell coatings on transition metal ceramic nanoparticle cores
Nanoparticles comprising a core including transition metal carbide, nitride, phosphide, sulfide, or boride and a noble metal shell can be made by transforming metal oxide core/noble metal shell materials coated in a ceramic material in a controlled environment. The noble metal shell can be a single monolayer. The self-assembly of metal carbide nanoparticles coated with atomically-thin noble metal monolayers results in a highly active, stable, and tunable catalytic platform.
1. A composition comprising: a plurality of nanoparticles, each nanoparticle independently comprising a transition metal ceramic core having a composition of formula (I):
M1 x M2 y M3 z X1 w1 X2 w2 (I)
wherein each of M1, M2 and M3, independently, is a transition metal element selected from 3d block or f block;
and each of X1 and X2, independently, is selected from the group consisting of C, B, and P, provided that at least one of X1 and X2 is selected such that the resulting compound is a boride, carbide, or phosphide of the transition metal;
wherein each of x, y, w1, w2, and z is a number between 0 and 3, where at least one of x, y, z, w1 and w2 is not zero and the combination of x, y, z, w1 and w2 completes the valence requirements of the formula; and
wherein M1, M2, or M3 further comprises Zr, Hf, Nb, or Ta;
the core having a uniform composition and a monolayer shell consisting of a noble metal in direct contact with the core, the core consisting of corrosion-resistant, and electrically conductive material with a melting point that binds to the noble metal shell and is insoluble in the noble metal lattice; and
each nanoparticle has a noble metal monolayer surface coverage ratio of 0.5-3.
2. The composition of claim 1 , wherein the shell further comprises Sn, Pb, or any combinations thereof.
3. The composition of claim 1 , wherein the size of the nanoparticle is no more than 10 nm.
4. The composition of claim 1 , wherein the size of the nanoparticle is no more than 5 nm.
5. The composition of claim 1 , wherein X1 is carbon, x is 1, w1 is 1, and y, z and w2 are zero.
6. The composition of claim 1 , wherein M1, M2, or M3 further comprises Zr.
7. The composition of claim 1 , wherein M1, M2, or M3 further comprises Hf.
8. The composition of claim 1 , wherein M1, M2, or M3 further comprises Nb.
9. The composition of claim 1 , wherein M1, M2, or M3 further comprises Ta.
10. The composition of claim 1 , wherein the noble metal is selected from Pd, Ru, Rh, Ir, Os and Ag.