A nitrogen-containing carbon material containing a nitrogen atom, a carbon atom, and a metal element X, in which the atomic ratio (N/C) of the nitrogen atom to the carbon atom is 0.005 to 0.3, the content of the metal element X is 0.1 to 20% by mass, and the average particle diameter is 1 to 300 nm.

A catalytic composition in particle form for making a gas diffusion electrode for an oxygen reduction reaction (ORR) has at least iron (Fe) in at least two different degrees of oxidation, optionally the at least two different degrees of oxidation being Fe and Fe.sub.2O.sub.3, and carbon (C). A gas diffusion electrode having the catalytic composition and a membrane-electrode assembly having the gas diffusion electrode are provided.

The nano-silicate composite according to various embodiments may include nano-silicon oxide, nano-silicon, and magnesium silicide between ion-conductive forsterite (Mg.sub.2SiO.sub.4), enstatite (MgSiO.sub.3), and magnesium disodium silicate (Na.sub.2MgSiO.sub.4) particles. A manufacturing method for the nano-silicate composite according to various embodiments may include mixing a silicate precursor, a metal reductant, and additives; and performing a mechano-chemical reaction by mixing the silicate precursor, metal reductant, and additives with beads. An electrode composition according to various embodiments may include the nano-silicate composite of the present disclosure. An electrode according to various embodiments may include the nano-silicate composite of the present disclosure.