Francisco Marques dos Santos Vieira1,Ismaila Dabo1,Raymond Schaak1,Zhiqiang Mao1,Rowan Katzbaer1
The Pennsylvania State University1
Francisco Marques dos Santos Vieira1,Ismaila Dabo1,Raymond Schaak1,Zhiqiang Mao1,Rowan Katzbaer1
The Pennsylvania State University1
Due to its high energy density, hydrogen fuel shows promise is the decarbonization of freight transport. However, there remain challenges in the synthesis of hydrogen fuel. Electrocatalytic water splitting holds the potential to sustainably produce hydrogen fuel provided suitable catalysts are identified. Here, we present the high entropy aluminate spinel oxide (Fe<sub>0.2</sub>Co<sub>0.2</sub>Ni<sub>0.2</sub>Cu<sub>0.2</sub>Zn<sub>0.2</sub>)Al<sub>2</sub>O<sub>4</sub> (<i>A</i><sup>5</sup>Al<sub>2</sub>O<sub>4</sub>) as catalyst for the for the oxygen evolution reaction (OER) in an alkaline electrolyte, and explore its electronic structure. In High entropy oxides (HEOs), numerous cations coexist in a single sublattice forming a solid solution throughout the crystalline solid. The sharing of a sublattice gives rise to unique, and even enhanced, properties including improved catalytic performance. Experimental measurements indicate <i>A</i><sup>5</sup>Al<sub>2</sub>O<sub>4</sub> has a bandgap far narrower than its parent phases. First principles calculations indicate that this narrowing of the bandgap is a consequence of the broadening of bands arising from the hybridization of the 3d states due to the variation of electronegativity across the 3d transition metal series. The observed narrowing of the bandgap in the high entropy spinel highlights a new method of engineering electronic structure using a high entropy approach to achieve desired material properties.