In-situ study of the hydrogen peroxide photoproduction in seawater on carbon dot-based metal-free catalyst under operation condition

Hydrogen peroxide(H_(2)O_(2))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/cm^(2)),the optimized catalyst of RUT-4 is stable and can achieve a high H_(2)O_(2)yield of 330.36μmol/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 H_(2)O_(2)photoproduction of RUT-4 under operation condition.RUT-4 has strong oxygen(O_(2))absorption capacity,and the O_(2)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 O_(2)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 H_(2)O_(2)photoproduction with metal-free catalysts in seawater.

Sulfonated carbon dots modified IrO_(2)nanosheet as durable and high-efficient electrocatalyst for boosting acidic oxygen evolution reaction

Oxygen evolution reaction(OER)plays a crucial role in developing energy conversion and adjusting electronic structure of the electrocatalysts can effectively improve the catalytic activity and stability.However,it is a challenge to adjust the electronic structure on two-dimensional iridium dioxide nanosheets(IrO_(2)NS),which have the advantages of high atom utilization.Here,we regulate the surface properties of IrO_(2)NS through sulfonated carbon dots(SCDs)to promote the OER catalytic process.The catalyst IrO_(2)NS/SCDs-2 exhibited excellent catalytic activity with a lower overpotential of 180 mV than IrO_(2)NS(230 mV)at the current density of 10 mA·cm^(-2)in a 0.5 M H2SO4 solution.And after 160 h of stability testing,the overpotential of IrO_(2)NS/SCDs-2 only decreased by 4 mV.Moreover,transient potential scanning test can visually demonstrate that the addition of SCDs improves the conductivity of the catalyst and increases the electron transfer rate.