Towards energy level cascaded "quantum armours" combating metal corrosion.

[Display omitted] • A unique nanotree-like quaternary superstructure is successfully prepared. • This multi-dimensional composite enhances solar absorption and carrier separation. • The unique quaternary composite realizes the high-performance PCP application. • Time-delay protection also could be realized due to the unique nanotree structure. • The PCP mechanism is clarified by DFT calculation. Stainless steels typically feature high toughness and good corrosion resistance. However, pitting corrosion can easily occur on stainless steel and the passivation film tends to be vulnerable under pressure or in brine environments. Metal corrosion is a long-standing challenge for the steel industry, forging a path to net-zero. Herein, by successive growth of a series of quantum confined nanocrystals such as quantum dots and nanorods with gradient band energy level alignment, high-performance photoelectrochemical cathodic protection for steel is demonstrated with remarkable mechanical and electrochemical stability. Under simulated solar light illumination, effective photoinduced protection can be realized for 304 stainless steel which enables long-term corrosion resistance in a 3.5 wt% NaCl solution. Unique nanotree-like structures and the quaternary material combination can store excess charges and release them gradually, enabling time-delay protection for metals after light excitation. Various promising functionalities as unique photoelectrodes can be envisioned arising from the proposed 3D nanotree morphology. [ABSTRACT FROM AUTHOR]