Ultra-small intermetallic NiZn nanoparticles: a non-precious metal catalyst for efficient electrocatalysis
Intermetallics are long-range order alloys synthesized traditionally via annealing the nanoparticles of a random alloy, resulting in the sintering of the nanoparticles that leads to the formation of polydispersed sample and thus remaining a challenge to achieve monodisperse tiny intermetallics. Herein, ultra-small monodisperse intermetallic NiZn nanoparticles were synthesized based on the low temperature solution chemistry route through the chemical conversion of metal nanoparticles into the order alloy using an organometallic zinc precursor. During the transformation of single metal nanoparticles to the corresponding alloys, the particles retained their morphology. The resulting order alloy with earth-abundant materials demonstrates high-performance electrocatalysis for oxygen evolution reaction (OER) with a low overpotential of 283 mV at a current density of 10 mA cm−2 and small Tafel slope of 73 mV dec−1, along with excellent stability and durability. Intermetallic NiZn exhibits outstanding OER efficacy compared to that of Ni0.7Zn0.3 alloy, pure Ni nanoparticles or even the state-of-the art RuO2. Their atomic ordering as well as the modification of the electronic structure of Ni upon alloying with Zn, together with atomic-scale synergistic effect produced from Ni and Zn lead to the enhanced intrinsic catalytic activity. The present findings point to a general route to produce nanoscale tiny alloys and also provide excellent electrocatalysts having exceptional energy conversion efficiency.