Inorganic　salts　have　been　widely　studied　as　templates　for　the　synthesis　of　2D　layer　structures.　However,　these　salts　normally　can　only　serve　as　templates　without　any　catalytic　activity.　Here,　we　report　that　LiCl　used　for　the　synthesis　of　ultrathin　nanosheets　not　only　serves　as　template　for　the　synthesis　of　ultrathin　Co2P　nanosheets　with　a　thickness　of　0.7　nm　but　also　acts　as　a　catalyst　that　induces　the　phase-transfer　from　CoP　to　Co2P.　The　Co2P　nanosheets　have　a　high　electrochemical　performance　for　oxygen　evolution　reaction.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim