Hierarchically porous nickel/carbon composite monoliths prepared by sol–gel method from an ionic precursor

Abstract

Utilizing a facile sol–gel reaction accompanied by phase separation, rigid monolithic nickel hydroxide-based xerogels and nickel/carbon composites with hierarchical porosity have been successfully fabricated. In the synthetic route starting from nickel chloride as a nickel precursor, trimethylene oxide acts as a gelation initiator to increase pH in a reaction solution. In addition, poly(acrylic acid) plays a double role as a phase separation inducer and as a co-constituent with nickel hydroxide to comprise continuous gel skeletons in the micrometer range. As a result, obtained xerogels possess well-defined macropores evidenced by microscopy observation and mercury porosimetry. Subsequent heat-treatment in air led to the crystallization of NiO at 300°C, while calcination under argon flow brought about the formation of nickel/carbon (Ni/C) composites with hierarchical pores and large specific surface area at temperatures higher than 300°C. This is the first report on the preparation of rigid monolithic xerogels and metal/carbon composite with well-defined macropores based on a metal salt precursor containing “divalent” cation.