Nanoporous nickel films on glass substrate by sol-gel technique

We report the sol-gel preparation of NiO films and their reduction to form nanoporous nickel films on glass substrate. Consisting of densely packed nanoparticles, the as-prepared NiO films are smooth and uniform. Nickel films with a nanoporous network-like structure are formed upon reductive annealing of NiO in hydrogen. The porosity of the nickel films is about 50%. The width of the pore is ca. 100 nm, and its length can reach hundreds of nanometers. The formation mechanism of nanoporous nickel films can be explained by the dewetting of nickel on a glass substrate driven by surface energy minimization.