Rational Phase Control in the Synthesis of Cobalt Sulfides

A library of substituted thioureas was used as sulfur reagents in the synthesis of cobalt sulfides. The substitution pattern of the thioureas controls the decomposition rate of precursors into sulfur monomers and thereby aids in the exploration of decomposition kinetics on cobalt sulfide-phase formation, including phase-pure jaipurite (CoS), cobalt pentlandite (Co₈S₉), linnaeite (Co₃S₄), and cattierite (CoS₂). We hypothesize that the available transformation pathways between phases during synthesis are dictated by the approximate ccp or hcp stacking of the sulfur lattice. Through gaining a complex understanding of the cobalt sulfide crystal system, phase-pure syntheses of all four naturally occurring crystalline structures in the cobalt sulfide system were achieved.