Nh4vo3

A total of 5 g urea (NH₂CONH₂, NIHON SHIYAKU REAGENT) was added into an aluminum crucible, and subsequent thermal treatment at 550 °C for 2 h with 5 °C min⁻¹ of heating rate in argon atmosphere could obtain a light-yellow powder composed of g-C₃N₄ nanoparticles. A total of 3.38 g bismuth (III) nitrate pentahydrate (Bi(NO₃)₃·5H₂O, Alfa Aesar) was placed in 40 mL of 2 M nitric acid solution (solution A). Then, 0-40 wt% g-C₃N₄ was put into solution A to be stirred for 1 h. The 0.81 g ammonium metavanadate (NH₄VO₃, Acros) was dissolved in 40 mL of deionized (DI) water (solution B). The 1 wt% surfactant, such as citric acid monohydrate (CIT, C₆H₈O₇•H₂O, fw: 192.12, SHOWA), (1-hexadecyl)trimethylammonium bromide (CTAB, CH₃(CH₂)₁₅N(CH₃)₃Br, fw: 364.42, Alfa Aesar), and polyethylene glycol (PEG, C_2nH_4n+2O_n+1, fw: 4,000, SHOWA), was added into the solution B. The 0-20 mol% copper (II) acetate monohydrate (Cu(CH₃COO)₂•H₂O, Merck) was also added in 20 mL of DI water (solution C). Subsequently, solution A and solution C were added into solution B. Then, the reaction mixture was treated with a sonochemical instrument (700 W, 20 kHz, Q700 SONICATOR) for 0.5 h–2 h at 60 °C [4 (link)]. Finally, the copper-doped BiVO₄/g-C₃N₄ samples were collected.

Bismuth(III) nitrate pentahydrate (Bi(NO₃)₃×5H₂O, VWR Chemicals, Paris, France), ammonium metavanadate (NH₄VO₃, Acros Organics, Geel, Belgium), ethylenediaminetetraacetic acid disodium salt dihydrate (EDTA-2Na, T.T.T., Sveta Nedjelja, Croatia), and nitric acid (HNO₃, Lach-ner, Czech Republic) were used for BiVO₄ synthesis. Ultrapure water from a Milli-Q system (Direct-Q3 UV, Merck Millipore, Burlington, MA, USA) was used to prepare all aqueous solutions. BiVO₄ was synthesized using a co-precipitation method [18 (link)]. Briefly, 0.2 M solutions of Bi(NO₃)₃×5H₂O and NH₄VO₃ were prepared in HNO₃ (1.5 M) and hot water (80 °C), respectively. A total of 0.382 g of EDTA was dissolved in 50 mL of Bi(NO₃)₃ solution. The precursor solutions were then mixed and stirred for one week at room temperature in a dark environment. BiVO₄ products were isolated using a centrifuge (EBA 21, Hettich Zentrifugen, Zürich, Switzerland) at a relative centrifugal force of 1370g × for 3 min, washed three times with ultrapure water, dried at 80 °C in a laboratory oven (UN-55, Memmert, Schwabach, Germany), and finally calcined at 450 °C for 2 h in a laboratory furnace (LP-08, Instrumentaria, Zagreb, Croatia).