Tunable Eg Orbital Occupancy in Heusler Compounds for Oxygen Evolution Reaction

Heusler compounds have great potential in electrocatalysis due to their mechanical robustness, metallic conductivity, and wide tunability in the electronic structure and element compositions. This study reports the first application of Co₂YZ type Heusler compounds as electrocatalysts towards oxygen evolution reaction (OER). A range of Co₂YZ crystals was synthesized through the arc-melting method and the e_g orbital filling of Co was precisely regulated by varying Y and Z sites of the compound. A strong correlation between the e_g orbital filling of reactive Co sites and OER activity was found on Co₂MnZ compounds (Z = Ti, Al, V, and Ga) whereby higher catalytic current was achieved with e_g orbital filling approaching to unity. A similar trend of e_g orbital filling on the reactivity of cobalt sites was also observed for other set of Heusler compounds (Co₂VZ, Z = Sn and Ga). This work demonstrates proof of concept of application of Heusler compounds as a new class of OER electrocatalyst and the influence of the manipulation of the spin orbitals on their catalytic performances.