The unifying Role of the “Oxo Wall” concept in Oxygen Evolution Catalysis

The rational design of catalytic active sites on the surface of solids enables efficient interfacial proton-electron transfer processes in the oxygen evolution reaction (OER) and is thus essential for high-performance water splitting on electrolyzer anodes. Popular examples of rational catalyst designs include the Sabatier principle associated with solid-state quantum-chemistry volcano-type reactivity predictions. The use of molecular unifying concepts to predict and rationalize the design of catalytic active OER sites on solid surfaces is rare. Here, we develop an a priori, chemically informed catalyst-design principle by transferring the oxo-wall concept of molecular coordination chemistry to bimetallic solid catalysts. The molecular “oxo wall” rule essentially states that tetragonal metal complexes with multi-bonded M=O ligands do not exist for metals to the right of group 8. We hypothesize that pairing metals located on opposite sides of the oxo wall creates complementary electronic functionality and leads to enhanced catalytic activity relative to combinations in which both metals lie on the same side. We show that this framework – although rooted in molecular ligand-field effects and developed and validated in coordination chemistry – is capable of predicting and rationalizing reactivity trends of solid-state mixed-metal layered double hydroxides OER catalysts. The very predictive character of the molecular “oxo wall” concept as to reactivity and stability of multiple-bond M-O cores makes it a unifying guiding principle for molecular and solid-state OER catalysis. We anticipate that the cross-disciplinary findings that bridge molecular chemistry and solid-state electrochemistry will help to better design of O 2 -based technologies with improved performance.