In-situ study of the hydrogen peroxide photoproduction in seawater on carbon dot-based metal-free catalyst under operation condition
Jiaxuan Wang, Jiacheng Li, Zenan Li, Jie Wu, Honglin Si, Yangbo Wu, Zhiyong Guo, Xuepeng Wang, Fan Liao, Hui Huang, Mingwang Shao, Yang Liu, Zhenhui Kang
Abstract
Hydrogen peroxide (H2O2) photoproduction in seawater with metal-free photocatalysts derived from biomass materials is a green, sustainable, and ultra environmentally friendly way. However, most photocatalysts are always corroded or poisoned in seawater, resulting in a significantly reduced catalytic performance. Here, we report the metal-free photocatalysts (RUT-1 to RUT-5) with in-situ generated carbon dots (CDs) from biomass materials (Rutin) by a simple microwave-assisted pyrolysis method. Under visible light (λ ≥ 420 nm, 81.6 mW/cm2), the optimized catalyst of RUT-4 is stable and can achieve a high H2O2 yield of 330.36 µmol/L in seawater, 1.78 times higher than that in normal water. New transient potential scanning (TPS) tests are developed and operated to in-situ study the H2O2 photoproduction of RUT-4 under operation condition. RUT-4 has strong oxygen (O2) absorption capacity, and the O2 reduction rate in seawater is higher than that in water. Metal cations in seawater further promote the photo-charge separation and facilitate the photo-reduction reaction. For RUT-4, the conduction band level under operating conditions only satisfies the requirement of O2 reduction but not for hydrogen (H2) evolution. This work provides new insights for the in-situ study of photocatalyst under operation condition, and gives a green and sustainable path for the H2O2 photoproduction with metal-free catalysts in seawater.