A novel porous Ni-alginate hybrid material was fabricated via a facile in-situ reduction of a Ni(II) alginate 3D hydrogel, which was obtained through the coordination of Ni(II) ions with sodium alginate, a natural polysaccharide. Notably, Ni(II) species first coordinated with Alg as the gelling agent during the construction of the 3D hydrogel and then were reduced to the active Ni(0) species in hybrid materials for hydrogenation. TEM results revealed that the Ni particles in Ni-alginate hybrid material were highly dispersed and in extremely small sizes, compared with those in the alginate supported Ni catalyst prepared by a conventional impregnation-reduction method. XPS and TGA results demonstrated the strong interaction between Ni and alginate in Ni-Alg-0 (where "Alg" represents sodium alginate and "0" represents the volume of water added in the NaBH4 solution during reduction), which suppresses agglomeration and prevents loss of the active species. This novel catalyst exhibited excellent catalytic activity and stability in styrene hydrogenation with no appreciable loss of its initial activity for up to 20 times of recycling. Furthermore, this material exhibited good catalytic activity in the hydrogenation of a number of unsaturated substrates as well. (C) 2017 Elsevier B.V. All rights reserved.