▎ 摘　　要

NOVELTY - Producing composite particle having core-shell structure comprises forming a graphene shell on the particles by contacting a carbon source with a composite structure including an inorganic matrix in which transition metal particles are spaced apart from each other. USE - The method is useful in producing composite particle for electrode, and catalyst (all claimed) for hydrogen generation reaction. ADVANTAGE - The method minimizes formation of composite particles having low-quality graphene shells, and excellent yield of high-quality graphene shells, and prevents formation of other carbon bodies due to side reactions. The composite particle has excellent catalytic performance, durability, long life, and electrochemical properties i.e. hydrogen generation rate and hydrogen generation rate, and does not requires use of binder to fix. DETAILED DESCRIPTION - An INDEPENDENT CLAIMSare also included for: (1) composite structure comprising inorganic matrix, and composite particles spaced apart from each other in the inorganic matrix. The composite particle comprises transition metal core and graphene shell surrounding the core; (2) composite particles comprising transition metal core, and a single layer graphene shell surrounding the core; (3) catalyst comprising composite particles with core-shell structure; and (4) electrode comprising catalyst.