Among the exfoliation processes applied on layered materials, it is the first time to explore the ultrasonic exfoliation in water for improving the catalytic properties of NiFe2O4/CB (CB = carbon black) nanospheres towards the electrocatalytic hydrogen evolution reaction (HER) in acidic media. It is found that after exfoliation, the overpotential of HER on NiFe2O4/CB nanospheres is improved by about 90 mV at a current density of 10 mA cm(-2). Moreover, the exfoliated NiFe2O4/CB nanospheres are not only more stable than the commercial Pt/C catalyst, but also they exhibit an overpotential improvement of about 100 mV at 50 mA cm(-2), after 6000 CV cycles. It is also found that the ultrasonic process causes uniformed NiFe2O4/CB particles, an increase of the electrochemical active sites, enriched Fe2+ ion and Fe3+ occupied on tetrahedral sites on the surface layer of the NiFe2O4/CB nanospheres, as resulted from the analysis with XPS, FTIR etc., leading to a higher activity and excellent durability. Furthermore, the approach also provides new insights on processing of materials in a green route. (C) 2020 Elsevier Ltd. All rights reserved.