Unravelling lewis acidic and reductive characters of normal and inverse nickel-cobalt thiospinels in directing catalytic H2O2 cleavage

Abstract

(Inverse) spinel-typed bimetallic sulfides are fascinating H2O2 scissors because of the inclusion of S-2, which can regenerate metals (M delta+,delta <= 2) used to produce (OH)-O-center dot via H2O2 dissection. These sulfides, however, were underexplored regarding compositional, structural, and electronic tunabilities based on the proper selection of metal constituents. Motivated by S-modified Ni delta+/Co delta+ promising to H2O2 cleavage, Ni2CoS4, NiCo2S4, NiS/CoS were synthesized and contrasted with regards to their catalytic traits. Ni2CoS4 provided the greatest activity in dissecting H2O2 among the catalysts. Nonetheless, Ni2CoS4 catalyzed H2O2 scission primarily via homogeneous catalysis mediated by leached Ni delta+/Co delta+. Conversely, NiCo2S4, NiS, and CoS catalyzed H2O2 cleavage mainly via unleached Ni delta+/Co delta+ tenabled heterogeneous catalysis. Of significance, NiCo2S4 provided Lewis acidic strength favorable to adsorb H2O2 and desorb (OH)-O-center dot compared to NiS and CoS, respectively. Of additional significance, NiCo2S4 provided S2- with lesser energy required to reduce M(delta+1-)+ via e- transfer than NiS/CoS. Hence, NiCo2S4 prompted H2O2 scission cycle per unit time better than NiS/CoS, as evidenced by kinetic assessments. NiCo2S4 was also superior to Ni(2)CoS(4)because of the elongated lifespan anticipated as( center dot)OH producer, resulting from heterogeneous catalysis with moderate Ni delta+/Co delta+ leaching. Furthermore, NiCo2S4 revealed the greatest recyclability and mineralization efficiency in decomposing recalcitrants via (OH)-O-center dot-mediated oxidation.