Fig. 4.

Current vs. potential curves of BiVO₄ thin film electrodes under visible light irradiation. Concentration of precursor solution and calcination temperature, (A) 200 mmol L^-1, 573 K, (B) 200 mmol L^-1, 623 K, (C) 20 mmol L^-1, 673 K, (D) 50 mmol L^-1, 673 K, (E) 100 mmol L^-1, 673 K, (F) 200 mmol L^-1, 673 K, (G) 300 mmol L^-1, 673 K, and (H) 200 mmol L^-1, 723; calcination time, 2 h. Electrolyte, 0.1 mmol L^-1 of an aqueous K₂SO₄ solution; sweep rate, 20 mV s^-1; light source, 300 W Xe-lamp with a cut-off filter (λ > 420 nm).