[Display omitted] • A novel step-scheme (S-scheme) heterojunction copper-indium-sulfide-modified polymeric carbon nitride (CuInS 2 /PCN) photocatalyst was synthesized. • CuInS 2 /PCN possess efficient charge separation and strong redox abilities based on S-scheme heterojunctions. • Superior photocatalytic hydrogen peroxide evolution performance over CuInS 2 /PCN was achieved under visible light irradiation. • S-scheme charge transfer mechanism between PCN and CuInS 2 was verified by photo-irradiated Kelvin probe force measurement. Photocatalytic oxygen reduction reaction (ORR) to produce hydrogen peroxide (H 2 O 2) has been regarded as an environmentally friendly strategy compared with the anthraquinone oxidation process. Superior photocatalytic activity strongly depends on the efficient separation of charge carriers. Herein, the step-scheme (S-scheme) heterojunction catalysts (CuInS 2 /PCN) over copper-indium-sulfide (CuInS 2) modified polymeric carbon nitride (PCN) were constructed via in-situ low-temperature hydrothermal method. The difference of Fermi levels between PCN and CuInS 2 promoted the spontaneously charge transfer directing from CuInS 2 to PCN, leading to the construction of built-in electric field at the interface. The S-scheme heterojunction was successfully formed on the effect of built-in electric field, whereby offered a new charge transfer route resulting in efficient migration and strong redox abilities of photogenerated electrons and holes. The optimized H 2 O 2 yield of 3CuInS 2 /PCN (1247.6 µmol·L−1·h−1) was nearly 11.6 and 16.0 times higher than PCN (107.4 µmol·L−1·h−1) and CuInS 2 (78.0 µmol·L−1·h−1), respectively, and the apparent quantum yield (AQY) for H 2 O 2 production over 3CuInS 2 /PCN reached 16.0 % at 420 nm. Photo-irradiated Kelvin probe force measurement revealed the S-scheme charge transfer mechanism between PCN and CuInS 2. This work offers a facile surface modification method for the design of photocatalyst in photocatalytic selective oxygen reduction reaction. [ABSTRACT FROM AUTHOR]