Photocatalytic oxygen reduction reaction over copper-indium-sulfide modified polymeric carbon nitride S-scheme heterojunction photocatalyst

Photocatalytic oxygen reduction reaction (ORR) to produce hydrogen peroxide (H2O2) 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 stepscheme (S-scheme) heterojunction catalysts (CuInS2/PCN) over copper-indium-sulfide (CuInS2) modified polymeric carbon nitride (PCN) were constructed via in-situ low-temperature hydrothermal method. The difference of Fermi levels between PCN and CuInS2 promoted the spontaneously charge transfer directing from CuInS2 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 H2O2 yield of 3CuInS2/PCN (1247.6 lmol.L-1.h-1) was nearly 11.6 and 16.0 times higher than PCN (107.4 lmol.L-1.h-1) and CuInS2 (78.0 lmol.L-1.h-1), respectively, and the apparent quantum yield (AQY) for H2O2 production over 3CuInS2/PCN reached 16.0 % at 420 nm. Photo-irradiated Kelvin probe force measurement revealed the S-scheme charge transfer mechanism between PCN and CuInS2. This work offers a facile surface modification method for the design of photocatalyst in photocatalytic selective oxygen reduction reaction.