Intrinsic Catalytic Activity for the Alkaline Hydrogen Evolution of Layer-Expanded MoS2 Functionalized with Nanoscale Ni and Co Sulfides

• Published in: ACS sustainable chemistry & engineering Vol. 10; no. 21; pp. 7117 - 7133
• Main Authors: Charnetskaya, Eleanora, Chatti, Manjunath, Kerr, Brittany V., Tran-Phu, Thanh, Nguyen, Tam D., Cherepanov, Pavel V., Hoogeveen, Dijon A., Johannessen, Bernt, Tricoli, Antonio, MacFarlane, Douglas R., Hocking, Rosalie K., Simonov, Alexandr N.
• Format: Journal Article
• Language: English
• Published: American Chemical Society 30.05.2022
• Subjects: ambient temperature; capacitance; catalysts; catalytic activity; cobalt; durability; electrochemistry; green chemistry; hydrogen production; microwave treatment; molybdenum; nickel; surface area; HER; Structure; Molybdenum sulfide; Electrochemical kinetics; Intrinsic activity
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.2c01243

The hydrogen evolution reaction (HER) under alkaline conditions is subject to significant kinetic limitations even with the most active platinum-based catalysts, while more affordable non-noble-metal-based catalytic materials present further challenges in terms of activity and durability in operation. To improve on these aspects, we present a new microwave-assisted synthetic route to fabricate sulfides of nickel and cobalt integrated into a layer expanded molybdenum sulfide (NiS x /MoS2 LE and CoS x /MoS2 LE), which efficiently catalyze H2 evolution in 1 M KOH. The use of the microwave-synthesis conditions enables the formation of nanoscale Ni and Co sulfides distributed homogeneously within the highly disordered layered molybdenum sulfide, as established using a comprehensive suite of physical methods. Synthesis of FeS x /MoS2 LE is also presented, but the resulting material did not exhibit promising properties. Electrocatalytic tests reveal higher activity of the Ni-based catalyst as compared to CoS x /MoS2 LE and especially unmodified MoS2 LE. The performance of NiS x /MoS2 LE at a HER overpotential of 0.15 V at ambient temperature and 60 °C corresponds to specific H2 evolution rates of 28 ± 4 and 58 ± 10 A g–1, respectively. Analysis of the electrokinetic data indicates that the exchange current density of the HER per an electrochemically active surface area of the sulfide-based materials is not high (∼0.001 mA cm–2 at ambient temperature), and that the high performance per unit mass observed here is supported by the well-developed surface area of the material (corresponding to a specific capacitance of ∼71 F g–1). A similar conclusion likely applies to many nickel and cobalt sulfide-based alkaline hydrogen evolution catalysts reported previously. Durability in operation of NiS x /MoS2 LE and CoS x /MoS2 LE is also demonstrated, in particular through a 2-week-long two-electrode water splitting test.