Engineering active heterojunction architecture with oxygenated-Co, Mo bimetallic sulfide heteronanosheet and graphene...

Bimetallic sulfides have distinctive catalytic property in activating peroxymonosulfate (PMS) for water remediation. Polyoxometalates as potential precursors have rarely been reported for the catalytic degradation of refractory organic pollutants. Herein, a composite catalyst of Co-Mo bimetallic sulfides supported onto graphene oxide (O-CoMoS/GO) with a heterojunction architecture was synthesized through a hydrothermal strategy with polyoxometalates ((NH₄)₄[Co^IIMo₆O₂₄H₆]·6H₂O) as the precursor and applied in the PMS activation. This material showed a superior performance for the catalytic degradation of the model organic pollutant, 4-chlorophenol (rapidly removed within 10 min with an apparent reaction rate constant of 0.5458 min^-1). O-CoMoS/GO outperformed most of the reported catalysts in terms of activity and had a strong tolerance towards common organic and inorganic compounds in water, and could perform well in different real water systems. Experimental and theoretical results indicated that the introduction of GO could achieve the enrichment of electrons on the metals and reduce the d band center (ε_d) of Co close to the Fermi level (ε_F), thereby facilitating the interfacial electron transfer process. The activation mechanism was due to the as-prepared bimetallic sulfides and the formation of heterojunction structure with GO, where Co(II) as the active center could be regenerated by the adjacent Mo element (as co-catalyst) and by gathering electrons from GO through the Co/Mo-O-C coupling. This work provides insights into the design of bimetallic sulfide catalysts in activating PMS for water remediation.