1,2-Bis-(diphenylphosphino)ethane (dppe) appended cobalt(iii)-dithiocarbamates as single source precursors of cobalt sulfide/cobalt phosphide composites: apt electrocatalytic materials for water splitting reactions

Abstract

New heteroleptic dppe appended Co(III)-dithiocarbamate (dtc) complex cations with compositions [Co(S₂CNEt₂)₂(dppe)](PF₆) (Co-Et), [Co(S₂CNPrⁱ₂)₂(dppe)](PF₆) (Co-Pr) and [Co(S₂CNBuⁿ₂)₂(dppe)](PF₆) (Co-Bu) have been synthesized and characterized by microanalysis, spectroscopic methods and crystallographic analysis. The single crystal X-ray diffraction results indicated that in all three complexes, the coordination environment around Co(III) is distorted octahedral and Co(III) is coordinated to four sulfur centers of the two dtc ligands and the two phosphorus centers of the dppe ligand. These complexes serve as precursors to yield cobalt sulfide/cobalt phosphide nano-composites ^dCo-Et, ^dCo-Pr and ^dCo-Bu by solvothermal decomposition of Co-Et, Co-Pr and Co-Bu, respectively. The decomposed materials have been characterized by PXRD and SEM-EDAX and explored as potential electrocatalysts for both oxygen evolution and hydrogen evolution reactions in basic and acidic media, respectively. Catalytic activity is dependent on the precursor complex and best OER and HER activities are observed for ^dCo-Bu with an η¹⁰ of 230 mV and a Tafel slope of 192.11 mV dec⁻¹ for the OER and an η¹⁰ of 470 mV and a Tafel slope of 126.21 mV dec⁻¹ for the HER.