Electronic impact of Ni₂P nanoparticle size on hydrogenation rates

Nickel phosphide, Ni₂P, nanoparticles supported on SiO₂ show a marked volcano shaped size dependence on hydrogenation of phenol. Kinetic analysis and physicochemical characterization shows the electron density of Ni to increase with increasing Ni₂P size, enhancing in turn the H₂ adsorption strength. For particles below 15 nm, H adsorbs weakly causing a low surface coverage of H, gradually increasing with particle size. For large particles, hydrogen binds too strongly causing a high coverage but low catalytic activity. The remarkable size dependence of the electronic properties show that Ni₂P particle size can be used to fine-tune its activity for hydrogenation.