Tailoring the electrocatalytic activity of multicomponent (Co,Fe,Ni)9S8-xSex pentlandite solid electrodes

The multi-component approach to materials design is gaining increasing popularity in energy-conversion-oriented applications. This study describes a 5-component multimetallic chalcogenide compound with a pentlandite structure that recently became increasingly interesting in terms of electrocatalytic water splitting. The solubility limit of Se in the trimetallic Co3Fe3Ni3S8 system was determined along with the potential effect of this additive on the material's intrinsic properties. This was followed by an unprecedented approach, an attempt to fabricate solid electrodes using the inductive hot-pressing method. The effects of the consolidation conditions on the morphology and final properties of the material are discussed in detail. Tailoring both the chemical composition and processing conditions (initial grain size, sintering temperature) can lead to the optimization of highly efficient electrocatalysts for water splitting. The best electrodes were characterized at elevated current densities of 120 mA cm-2, showing low overpotentials (240 mV versus RHE) but with rather low electrochemical active surface area and moderately optimal reaction kinetics. It was therefore shown that using multi-component compositions resulted in good intrinsic properties of the materials toward hydrogen production, together with high density and vacancy concentrations provided by the sintering process, thus producing an efficient electrocatalyst using a simple, scalable method without any additional processing.