Taking Advantage of Teamwork: Unsupported Cobalt Molybdenum Sulfide as an Active HER Electrocatalyst in Alkaline Media

A bimetallic cobalt molybdenum sulfide (Co0.5Mo0.5Sx) material was studied as candidate electrocatalyst to replace platinum-based cathode for HER reaction in alkaline media. The Co0.5Mo0.5Sxwas obtained from a hydrothermal synthesis methodology employing sodium diethyldithiocarbamate as sulfurizing agent, a non-conventional compound. The recovered sulfide material was physicochemically characterized by XRD, Raman spectroscopy, TEM and XPS measurements. Analogous monometallic sulfides were also synthesized to compare their HER activities to that of Co0.5Mo0.5Sx. Such electrochemical characterization was performed by the application of polarization and EIS analyzes in 1 M KOH. An evident synergistic effect emerged in the bimetallic sulfide and it was associated with the design of a catalyst less susceptible to air-oxidation added to the roles performed by cobalt- and molybdenum-based species in the HER mechanism. Finally, a physical mixture of Co0.5Mo0.5Sxand Carbon Vulcan was prepared aiming to enhance the electronic conductivity of the electrode. As result, an overpotential of 131 mV was requested to achieve −10 mA cm−2. In addition, to achieve −200 mA cm−2, this electrode only needed an overpotential 66 mV higher than the one necessary for the benchmarking 40% Pt/C electrocatalyst.