N-doped carbon materials produced by CVD with the compounds derived from LDHs

Abstract

Layered double hydroxides (LDHs) of various compositions, i.e. Mg–Al, Mg–Mn–Al, are applied as the precursors of metal oxides for the preparation of N-doped carbon materials via chemical vapour deposition (CVD) with acetonitrile (as carbon and nitrogen source) at 600 and 700 °C. The use of Mn-containing LDHs for the preparation of the carbon materials is a novelty. The impact of transition metal species, i.e. MnxOy, in a blend of metal oxides derived from LDHs on the amount of carbon deposit and its composition, morphology, textural and capacitive properties is investigated. Mn-containing species occurring in a mixture of metal oxides enhance the quantity of carbonaceous product compared to those derived from Mg–Al LDHs. Thermally heated Mg–Mn–Al LDHs contain structural defects due to manganese oxides, which promote the formation of carbon deposit, especially higher production of amorphous carbons. The addition of Mn into Mg–Al LDHs matrix leads to carbon particles with increased N-doping and enhanced volume of mesopores. Furthermore, graphitic domains occurring in the carbon materials obtained with Mg–Mn–Al LDHs are thicker than those in the corresponding samples obtained with Mg–Al LDHs as Mn-containing species influence the concentration and location of N-containing groups in graphitic array. The specific capacitance of the carbon materials produced by CVD with the compounds derived from Mg–Al LDHs or Mg–Mn–Al LDHs is comparable (20–25 μF cm−2). The formation of electrical double layer at electrode/electrolyte interface is easier for the carbon materials prepared at 700 °C than for the carbon materials prepared at 600 °C. The maximum charge is stored either in the shallow parts of carbon particles for the former, as they contain bottleneck mesopores, or in the deep parts of carbon particles for the latter, as they contain slit-shaped mesopores.Graphical abstract