Manifestation of Concealed Defects in MoS2 Nanospheres for Efficient and Durable Electrocatalytic Hydrogen Evolution Reaction

MoS2 nanospheres were formed using a template free hydro-thermal process, which exhibit high catalytic activity towards hydrogen evolution reaction (HER). The extend of defect sites are probed by extended X-ray absorption fine structure which found decrease in co-ordination number at Mo site rather than at S site. DFT calculations identified an uneven strain and defect distribution between two S planes of curved MoS2. Based on hydrogen adsorption on various sites, we identify a new pathway called extended activity @ shielded defects, for Volmer-Tafel and Volmer-Heyrovsky mechanisms, where H adsorption occurs at exposed S layer driven by defects in underneath S layer of nanosphere. Having higher defect concentration it exhibited excellent HER activity with overpotential of -0.12V, Tafel slope of 90 mV/decade, and higher turnover frequency. Our findings provide an avenue to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications.