Bi-Metallic Electrocatalysts for the Hydrogen Evolution Reaction

Ni atoms are broadly recognized as excellent water dissociation centers, while Mo atoms have superior adsorption properties towards hydrogen. Therefore, Mo-Ni-based bimetallic electrocatalysts are candidates for high-performance hydrogen evolution. In this project, nanocuboid NiMoO4 precursor is synthesized by hydrothermal method, and then the precursor is reduced in hydrogen or nitridated in ammonia. The nitridated NiMoO4 electrocatalyst shows relatively high current density in hydrogen evolution reaction, compared with Pt wire and reduced NiMoO4 electrocatalyst.

Figure (A): SEM image of nanocuboid NiMoO4. (B): Cyclic voltammetry of the synthesized catalyst and the standard Pt wire.

High Entropy Electrocatalysts for the Ammonia Oxidation Reaction

This project aims to utilize ammonia as part of the next generation of clean energy infrastructure. Liquid ammonia boasts a high energy density and can be utilized without producing greenhouse gases at room temperature via electrocatalytic oxidation, which can theoretically be performed at 0.1V. It can be utilized as both a hydrogen carrier, or directly in an ammonia fuel cell. Our work aims to discover effective electrocatalysts to split ammonia for hydrogen generation. High entropy catalysts, which are materials consisting of 5 or more elements in concentrations of 5-35 at% with uniform distribution, are prime candidates for this reaction. Advantages of these catalysts include enhanced stability, tunability/advanced active site engineering, and facile synthesis approaches using earth-abundant transition metals.

Fig. A: SEM image of the high entropy spinel oxide catalyst MnFeCoNiCuO, synthesized via a layered double hydroxide mediator.

Fig. B: Cyclic voltammetry and chronoamperometry of the synthesized catalyst. It achieved a current density of 15 mA/cm2 at 1.3V vs NHE , and an onset overpotential of 0.7V, which is 0.15V lower than that of the most active single metal oxide. Greater than 90% of current density was retained after 1 hour under reaction conditions.