Selenium tethered copper phthalocyanine hierarchical aggregates as electrochemical hydrogen evolution catalysts

Abstract

The development of non-precious metal catalysts for the hydrogen evolution reaction (HER) with excellent stability and adequate performance characteristics in an acid environment is of fundamental importance for inexpensive hydrogen production from renewable resources. In this work, n-octylselanyl (n-OctSe) substituted copper phthalocyanine (CuPc) hierarchical aggregates were prepared and evaluated as an efficient catalyst for the electrochemical HER. Selenoxide elimination performed on (n-OctSe)₈-CuPc with H₂O₂ under two different reaction conditions, one in MeOH/DCM medium at room temperature and another in toluene at 140 °C, led to the formation of nanostructured fibrous aggregates (FAs) and particulate aggregates (PAs), respectively. The structural and morphological characteristics of the prepared hierarchical aggregates have been systematically studied, thereby the coexistence of covalent and non-covalent linkage between CuPc skeletons is demonstrated by an adaptive structural ordering at the nanoscale regime. Owing to the unique structural order of hierarchical aggregates, the electrocatalytic HER overpotential (η) and interfacial charge transfer characteristics are greatly influenced. The nanostructured PAs exhibited much lower HER overpotential (−0.172 V) at a current density of 10 mA cm⁻² as compared to the HER overpotential of the state-of-art materials that come under polymeric coordination complexes and pristine-metal organic frameworks (MOFs). Accompanied by high stability under acidic conditions, the high-performance catalytic behavior of PAs shows promise for the development of novel non-precious metal catalysts.