Applicability of conventional protocols for benchmarking of unidirectional and bidirectional multi-electron homogeneous molecular catalysts beyond the pure kinetic regime

Accurate and rational benchmarking of molecular catalysts is essential to achieve high selectivity and efficiency towards electrochemical reactions associated with key energy and environmental challenges. Homogeneous catalytic schemes commonly involve intricate multi-electron, multi-step processes, the behaviour of which can depart significantly from that of the paradigmatic first-order one-electron catalytic mechanism (EC’ scheme). Nevertheless, currently, the quantitative analysis of such complex processes is mostly based on methods developed for the EC’ case. Since no general theoretical framework has been proposed for multi-electron multi-step processes, the degree of applicability of such protocols is unknown. This is investigated in this work by modelling the voltammetry of unidirectional and bidirectional two-electron catalysts (EEC’-type mechanisms). It is demonstrated that so-called pure kinetic (PK) conditions could be difficult to attain in the case of multi-electron catalysts so that the widely-used PK-based protocols of benchmarking can yield inaccurate results. In order to overcome this issue, novel suitable tools are presented.