Cobalt 2 acetate tetrahydrate

Bulk MoS₂ (powder), N-Methyl-2-pyrrolidone (NMP) (anhydrous, 99.5%), cobalt(II) acetate tetrahydrate (99%), iron(II) acetate (95%) and nickel(II) acetate tetrahydrate (98%) were purchased from Merck. PLA was obtained from Goodfellow. Hydrogen peroxide (30%) and ethanol (96%) were purchased from Chempur. Gaseous nitrogen and ethylene were purchased from Messer and Air Liquide, respectively.

Briefly, 20 mL melamine (Alfa Aesar) solution (2 mg mL⁻¹ in aqueous phase) was first mixed with 20 mL GO solution (4 mg mL⁻¹ in aqueous phase, prepared by a modified Hummers method) by stirring at 700 rpm for 15 min. Then, phosphomolybdic acid hydrate (27.4 mg, 0.015 mmol [H₃PMo₁₂O₄₀]⋅x H₂O (=PMo₁₂), Alfa Aesar) and Cobalt(II) acetate tetrahydrate (Co(OAc)₂⋅4 H₂O, Merck, containing 44.8, 22.4 and 14.9 mg (0.18, 0.09 and 0.06 mmol) for composite 2, 3 and 4) were dissolved in 40 mL H₂O and added to the above mixture under stirring at 1000 rpm for 6 h. Afterwards, the obtained mixtures were hydrothermally reacted at 180 °C for 12 h, and then cooled down to room temperature. The obtained solid composites were filtered off, washed with water for three times, and dried at 80 °C for overnight. Finally, the dried composites were calcined in the tube furnace programmed with two heating steps under Ar atmosphere, first at 400 °C for 2 h with a heating rate of 1 °C min⁻¹, and then at 800 °C for 2 h with a heating rate of 2 °C min⁻¹. This gave the final composites 2, 3, and 4 with the Mo/Co molar ratio of 1:1, 2:1 and 3:1, respectively. For comparison, we also prepared the catalyst 1 without adding Co(OAc)₂⋅4 H₂O, and the other conditions were kept the same.