Peaks and pitfalls of electrocatalytic descriptor models at the example of CO2 reduction
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Electrocatalysis advances rely on the development of efficient catalysts. Systematic material design hinges on identifying activity and selectivity descriptors. While adsorption energy descriptors have helped predict new materials, they are typically based on pure metals, uncertain of their applicability to complex materials like alloys. Here, we systematically analyze the validity of descriptor models for the electrochemical reduction of CO 2 (CO 2 RR). For this, we prepare gold, silver, and palladium alloys of variable composition and confirm experimentally the continuous variation of the d-band center (i.e. the CO adsorption energy) and work function (i.e. the potential of zero charge). Our results indicate that while the d-band center is the decisive factor for CO production, it, along with the work function, fails to fully explain the production of HCOO − and H 2 . Designing a copper-like alloy based on the matching of these descriptor values showed no formation of C 2 products (as commonly expected for copper). This breakdown of the descriptor model is explained from first-principles calculations by the heterogeneity of the surface leading to different deactivation pathways for C 2 product formation. Our results highlight the problems in transferring conventional descriptor models to more complex, heterogeneous materials motivating future developments.