Electrocatalysis and activity descriptors with metal phthalocyanines for energy conversion reactions

Abstract

• This review highlights the fundamental roles of metallo-phthalocyanines for various electrocatalysis. • Discussion on activity descriptors for various electrocatalysis with metallo-phthalocyanines. • Summary on the going reports on metallo-phthalocyanines for energy applications. • Discussion on strategies to benchmark to performance of MN4-molecular electrocatalysts. • The difficulties and future directions for the metallo-phthalocyanines based materials at practical level. Metal phthalocyanines (MPcs) and their derivatives are not only considered as potential electrocatalysts for oxygen reduction reaction (ORR), oxygen and hydrogen evolution reaction (OER and HER) and carbon dioxide reduction reaction (CO 2 RR) but also as ideal models to understand the origin of activity of various electrocatalysts. The volcano correlations are usually used to understand the inception of synergistic reactivity of molecular electrocatalysts that the appropriate binding strength of reaction intermediate is essential. The M(III)/(II) redox potential, which was found to be the key activity descriptors for ORR process, while M(IV)/(III) and M(II)/(I) redox couples for OER, HER, and CO 2 RR, respectively. The aim of this review is (i) to simplify the existing bridges between the quantum parameters of MPcs and their activities, (ii) to highlight the recent advancements on MPcs-based materials for ORR, OER, HER and CO 2 RR, and (iii) to emphasize the future aspects from the combined approach of molecular, supramolecular and material science engineering for above mentioned electrocatalysis. The efforts in this work presents the “systematic design principles” which may be useful for researchers in constructing electrode materials for energy processes.