On the Optimization of Nitrogen‐Reduction Electrocatalysts: Breaking Scaling Relation or Catalytic Resonance Theory?

Electrochemical nitrogen reduction reaction (NRR) is mainly hampered by two facts. On the one hand, the hydrogen evolution reaction competes with the NRR under cathodic reaction conditions. On the other hand, the sluggish reaction kinetics of the NRR, due to the transfer of six proton-electron pairs in the reaction mechanism, causes large overpotentials, and thus results in humble intrinsic activity for ammonia formation. Optimization strategies for NRR electrocatalysts are ultimately called for to overcome these issues. While breaking scaling relation is considered as a universal remedy to enhance turnover for any electrocatalytic process, recently, the concept of catalytic resonance theory has been put forth as a second option to obtain reaction rates beyond the limiting Sabatier volcano. Yet, a comparison of these two concepts is missing but urgently needed to comprehend design principles for electrocatalyst optimization on the atomic scale. In the present work, breaking scaling relation and catalytic resonance by programmable catalysis are compared on the example of the NRR over transition-metal oxides. It is demonstrated that a fine tuning rather than a full breaking of nitrogen-containing scaling relations is required to enhance electrocatalytic activity of electrocatalysts at the volcano apex. The success of catalytic resonance theory is based on the occurrence of negative scaling correlations whereas in the case of positive scaling correlations, the impact of this approach on the optimization of electrocatalysts strongly depends on the location of the material in the volcano plot. The obtained insight may spur the development of NRR electrocatalysts with enhanced intrinsic activity by following the outlined design principles. in press