Unraveling Janus-like behavior of copper phosphide for selective production of reactive oxygen species: Singlet oxygen versus hydroxyl radical

•The Janus-like CuxP enables the selective production of reactive oxygen species.•The self-dissolution of CuxP at pH 3 in the dark produces hydroxyl radicals.•Singlet oxygen is mainly generated on CuxP at pH 7 under visible light irradiation.•Repeated use of CuxP at pH 3 in the dark is difficult.•The stability of CuxP is enhanced at pH 7 under visible light irradiation.