Hydrogen Peroxide Production with High Solar to Chemical Conversion (0.16%) and Efficient Water Purification Using Carbon Quantum Dots-Modified Indium Sulfide

Photocatalytic production of hydrogen peroxide (H2O2) is the need of the hour for green synthesis and sustainability. Herein, we designed hierarchical carbon quantum dots (CQDs)-supported β-indium sulfide (β-In2S3) nanoflakes as an efficient catalyst for H2O2 generation via a two-electron oxygen reduction reaction. The composite material exhibited a high H2O2 production rate of 634 μM h–1, a solar-to-chemical conversion (SCC) efficiency of 0.16%, a high forward rate constant of ∼19 μM min–1, and a low H2O2 dissociation constant of ∼0.004 min–1, all of which are significantly higher than those of pure β-In2S3. Moreover, this material also manifested good water remediation photocatalytic performance by way of removal of 93% chromium(VI), 58% nickel(II), and 94% rhodamine B in 2 h. The apparent rate constant for chromium(VI) reduction of the composite was 0.023 min–1, which is 10-fold higher than that of the pure material. β-In2S3-CQDs exhibited superior results, which can be attributed to their large electrochemical surface area, good light harnessing ability, upconverted photoluminescence, and the ability to act as an electron reservoir preventing recombination.