Amorphous MoSx developed on Co(OH)2 nanosheets generating efficient oxygen evolution catalysts

Exploration of high-efficiency and inexpensive electrocatalysts for the oxygen evolution reaction (OER) is of great importance for the design of renewable energy storage and conversion devices. Herein, we prepared amorphous MoSx-encapsulated Co(OH)2 nanosheets (aMoSx/Co(OH)2 NSs) as strongly robust and active OER electrocatalysts via a three-step procedure: first, Co(OH)2 nanosheets with catalytically active octahedral MO6 structures were synthesized by the hydrothermal process; second, violent ultrasonication was applied to exfoliate individual nanosheets from stacked Co(OH)2 sheets and break them down into smaller sheets and attach MoS42− ions uniformly on the nanosheets; third, MoS42− ions were thermally decomposed into amorphous MoSx on the Co(OH)2 nanosheets. The role of the incorporation of the amorphous MoSx nanostructure was to enhance the surface hydrophilicity for the availability of H2O and accelerate the electron transport capability for kinetic activities. Furthermore, the interaction between MoSx and Co(OH)2 is proposed to induce electron transfer from amorphous MoSx to Co(OH)2, which will promote the basic environment for cobalt sites, break the Co–O bond, favor the release of O2 molecules, and thus enhance the OER process. Optimization of the Co/Mo molar ratio demonstrated that aMoSx/Co(OH)2 NSs with the Co/Mo molar ratio of 8 had the best OER activity and delivered the overpotential of 350 mV at the current density of 10 mA cm−2 and the Tafel slope of 65.4 mV dec−1 in 0.1 M KOH. This study enriches the research on non-first-row (3d) metal incorporation for high-efficient OER catalysts and offers an alternative to noble metal catalysts.