Nanoporous Ni with a tunable nanopore size and chemical compositions was fabricated by dealloying a Ni30Mn70 precursor alloy at various temperatures. The influence of electrochemical parameters on the formation of large-scale nanoporous Ni was systematically investigated. Different from the fabrication of nanoporous noble metals (Au, Pt and Pd), the dealloying of Ni30Mn70 includes three kinetically competitive processes: dissolution of Mn, interface diffusion of Ni and dissolution of Ni. The nanopore size and residual Mn can be tailored by controlling the dealloying time, temperature and applied potential. The as-dealloyed nanoporous Ni with a large internal surface area, excellent conductivity and naturally formed oxide surface can be directly used as a free-standing electrode for electrochemical supercapacitors with a high capacitance and excellent cycling stability. (C) 2013 Elsevier B.V. All rights reserved.