Combinatorial Screening of Electronic and Geometric Effects in Compositionally Complex Solid Solutions Toward a Rational Design of Electrocatalysts

Alloying dissimilar elements presents an effective strategy for enhancing the electrocatalytic properties of multi-metal materials. This enhancement can be attributed to the modification of electronic and geometric effects, which play a crucial role in determining the overall electrocatalytic performance. However, these effects are intricately intertwined and often interrelated due to their coexistence. As a result, the improved catalytic performance of multi-metal systems is frequently attributed to synergistic or "cocktail" effects, without clear explanations of the role of alloying and the individual contribution of each element. A high-throughput experimentation approach is employed to investigate 342 compositions within the quaternary thin film system PdAgCuFe. The substitution of Cu with Fe (different number of valence electrons) or Ag (different atomic sizes) allows for selective manipulation of electronic or geometric effects, respectively. The substitution of Ag with Fe allows for the simultaneous variation of both effects. The number of valence electrons per unit cell volume is used as a descriptor for electrocatalytic activity, specifically with respect to the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), which can be optimized through independent or simultaneous alteration of electronic and geometric effects. The electrocatalytic properties of multi-metal materials are determined by electronic and geometric parameters, which are intricately intertwined. This research investigates the interplay between these parameters, using the quaternary PdAgCuFe thin-film system as a platform. The established correlation between valence electron density and catalytic activity provides insights for optimizing electrocatalysis through independent or simultaneous manipulation of electronic and geometric parameters.image