Nanostructured NiCo₂O₄/BiVO₄ Heterojunctions for Visible-Light Photocatalytic H₂O-to-H₂O₂ Synchronized Organic Pollutant Oxidation

Abstract

Photocatalytic H 2 O 2 generation using unlimited solar energy for in situ oxidation of organic pollutants in wastewater has been environmentally attractive. Photocatalytic H 2 O-to-H 2 O 2(aq) reaction by BiVO 4 , however, suffered from relatively low yields (e.g., 24 μM h −1 ) under visible-light irradiation, mainly due to its high recombination rate of charge carriers. Herein, nanostructured NiCo 2 O 4 /BiVO 4 Z-scheme heterojunctions were prepared to increase the oxygen reduction reaction for a higher H 2 O 2 yield rate (than BiVO 4 by 16 times approximately). Additionally, highly reactive superoxide ( • O 2 − ) and hydroxyl ( • OH) radicals from the photocatalytic H 2 O-to-H 2 O 2 process enhanced oxidation of a representative organic pollutant (i.e., methylene blue) under visiblelight irradiation. The photocatalytic oxidation rate constant was as high as 2 × 10 −7 M −1 s −1 . This visible-light photocatalytic H 2 O-to-H 2 O 2 synchronized oxidation of an organic pollutant by the nanostructured NiCo 2 O 4 /BiVO 4 heterojunctions demonstrates the possibility for a potential energy self-sufficient organic wastewater treatment process.

Enhanced Visible-Light H2O2 Production over Pt/g-C3N4 Schottky Junction Photocatalyst

“…1.64 and 1.67 V (vs NHE), respectively. The VB potentials for both samples are more positive than H 2 O/O 2 (+1.23 V vs NHE), but they are lower than H 2 O/H 2 O 2 (+1.76 V vs NHE) and H 2 O/ • OH (+2.73 V vs NHE) . As a result, photogenerated holes cannot be used to produce H 2 O 2 through the water oxidation route, but they can oxidize H 2 O to form O 2 and provide a reactant for H 2 O 2 production.…”

Enhanced photocatalytic activity of Ag2S particle decorated S-doped WO3 nanorods synthesized through two-stage vaporous vulcanization processes

“…Therefore, the photogenerated electrons and O 2 can react to form H 2 O 2 as an intermediate species in the reaction mechanism. 63 Moreover, the photogenerated holes can oxidize water molecules or hydroxide ions to form ˙OH radicals. The charge transfer mechanism and the redox reactions involved with photogenerated carriers in SWAS100 herein are similar to direct a Z-scheme photocatalyst composed of Ag 2 S nanoparticles and a hexagonal WO 3 rod template and Z-scheme Ag 2 S nanoplate/Bi 2 O 3 microrod composites.…”

Photocatalytic splitting of H2O-to-H2O2 by BiOI/g-C3N4/CoP S-scheme heterojunctions

“…Concentrations of H 2 O 2 during photocatalysis were determined by colorimetric spectroscopy using the copper-DMP method. 24 Typically, 2,9-dimethyl-1,10-phenanthroline (DMP) (0.5 mL) in ethanol (10 g L −1 ) was mixed with copper( ii ) sulfate pentahydrate (0.5 mL, 0.01 M, 98.0%, Sigma-Aldrich) and phosphate buffer (0.5 mL, 1 M, pH 7, Sigma-Aldrich) in deionized water (1 mL). The mixed solution was measured at 454 nm on a UV-Vis spectrometer (Cary 100, Varian).…”