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The main challenge for acidic water electrolysis is the lack of active and stable oxygen evolution catalysts based on abundant materials, which are globally scalable. Iridium oxide is the only material which is active and stable. However, Ir is extremely rare. While both active materials and stable materials exist, those that are active are usually not stable and vice versa. In this work, we present a new design strategy for activating stable materials originally deemed unsuitable due to a semiconducting nature and wide band gap energy. These stable semiconductors cannot change oxidation state under the relevant reaction conditions. Based on DFT calculations, we find that adding an n-type dopant facilitates oxygen binding on semiconductor surfaces. The binding is, however, strong and prevents further binding or desorption of oxygen. By combining both n-type and p-type dopants, the reactivity can be tuned so that oxygen can be adsorbed and desorbed under reaction conditions. The tuning results from the electrostatic interactions between the dopants as well as between the dopants and the binding site. This concept is experimentally verified on TiO2 by co-substituting with different pairs of n- and p-type dopants. Our findings suggest that the co-substitution approach can be used to activate stable materials, with no intrinsic oxygen evolution activity, to design new catalysts for acid water electrolysis.

Developing new efficient catalyst materials for the oxygen evolution reaction (OER) is essential for widespread proton exchange membrane water electrolyzer use. Both RuO

Developing new efficient catalyst materials for the oxygen evolution reaction (OER) is essential for widespread proton exchange membrane water electrolyzer use. Both RuO2 (110) and IrO2 (110) have been shown to be highly active OER catalysts, however DFT predictions have been unable to explain the high activity of RuO2. We propose that this discrepancy is due to RuO2 utilizing a different reaction pathway, as compared to the conventional IrO2 pathway. This hypothesis is supported by comparisons between experimental data, DFT data and the proposed reaction model. Furthermore, our findings indicate that the reaction pathway utilized by RuO2 (110) might be pH dependent, following the conventional pathway at high pH.

Pyrochlore oxides (A2B2O7 ) simultaneously containing iridium and ruthenium in the B-site are promising catalysts for oxygen evolution reaction (OER) in acid media. The catalytic activity of the pyrochlore basedcatalysts is increased by the coexistence of Ir and Ru in the B-site of the pyrochlore structure. Lanthanide(Yb, Gd, or Nd) stabilized mixed pyrochlores with a fraction of Ru in the B-site of x Ru = 0.2, 0.4, 0.6, 0.8were synthesized by the spray-freeze freeze-dry approach. All prepared mixed pyrochlore catalysts aresurpassing the OER activity of the corresponding iridium and ruthenium analogues featuring no cationmixing as well as that of the benchmark IrO2 catalyst. The synergy of Ir and Ru in the B-site of thepyrochlore structure suppresses the effect of the A-site cation radius on the OER activity. The observedOER activity scales with the Ir-Ru bond distance which represents the local structure of the preparedmaterials. The most active ytterbium catalyst also shows a significant stability improvement under OERoperando conditions over the benchmark IrO2&nbsp

Rational optimization of the OER activity of catalystsbased on LaNiO3 oxide is achieved by maximizing the presence of trivalent Ni in the surface structure. DFT investigations of the LaNiO3catalyst and surface structures related to it predict an improvement inthe OER activity for these materials to levels comparable with the topof the OER volcano if the La content is minimized while the oxidationstate of Ni is maintained. These theoretically predicted structures ofhigh intrinsic OER activity can be prepared by a templated spray-freeze freeze-drying synthesis followed by a simple postsynthesisexfoliation-like treatment in acidic media. These nanocrystallineLaNiO3-related materials confirm the theoretical predictions, showinga dramatic improvement in OER activity. The exfoliated surfacesremain stable in OER catalysis, as shown by an in-operando ICP-OESstudy. The unprecedented OER activation of the synthesized LaNiO3-based materials is related to a close juxtaposition of the theoretical conception of ideal structural motifs and the ability to engendersuch motifs using a unique synthetic procedure, both principally related to stabilization and pinning of the Ni oxidation state within the local coordination environment of the perovskite structure.

Developing new efficient catalyst materials for the oxygen evolution reaction (OER) is essential for widespread proton exchange membrane water electrolyzer use. Both RuO2(110) and IrO2(110) have been shown to be highly active OER catalysts, however DFT predictions have been unable to explain the high activity of RuO2. We propose that this discrepancy is due to RuO2 utilizing a different reaction pathway, as compared to the conventional IrO2 pathway. This hypothesis is supported by comparisons between experimental data, DFT data and the proposed reaction model.

Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups. Despite the substantial efforts, the driving force required for water oxidation is largely making the reaction inefficient. In the present work, we collected published studies involving DFT calculations for the OER, with the purpose to understand why the progress made so far, for lowering the overpotential of the reaction, is relatively small. The data revealed that the universal scaling relationship between HO* and HOO* intermediates is still present and robust, despite the variety in methods and structures used for calculating the binding energies of the intermediates. On the other hand, the data did not show a clear trend line regarding the O* binding. Our analysis suggested that trends in doped semiconducting oxides behave very differently from those in other oxides. This points towards a computational challenge in describing doped oxides in a realistic manner. We propose a way to overcome these computational challenges, which can be applied to simulations corresponding to doped semiconductors in general., Multiple strategies to overcome the intrinsic limitations of the oxygen evolution reaction (OER) have been proposed by numerous research groups.