Highly crystalline Ni/NiO hybrid electrodes processed by inkjet printing and laser-induced reductive sintering under ambient conditions.

In this study, we perform drop-on-demand (DOD) inkjet printing and laser reductive sintering of precrystallized NiO nanoparticle (NP) ink under ambient conditions to obtain NiO/Ni hybrid electrode patterns on a highly localized area. By formulating an inkjet-printable and laser-reducible NiO NP ink, and by exploring the optimum conditions of inkjet printing parameters, we generate stable droplets, enabling arbitrary shapes of NiO NP dot arrays or line patterns to be deposited. Subsequent short-time low-temperature sintering produces highly crystalline NiO electrodes. Furthermore, laser reductive sintering applied on deposited NiO NP patterns can successfully realize a selective transformation of NiO into Ni electrodes under ambient conditions. Therefore, we can define either NiO or Ni electrodes, or a combination of the two on specific areas with precise amounts of ink. In addition, we identify the characteristics of the synthesized NPs, NP ink, NiO and Ni electrodes using various analytical methods.