Photocatalytic generation of hydrogen under visible light on La2CuO4

The semiconducting properties of La 2 CuO 4 prepared by a chemical route are investigated for the first time by the photo-electrochemical technique. The optical gap is found to be 1.27 eV and the transition is directly allowed. p-Type conductivity is demonstrated from the Mott–Schottky plot in alkaline KOH solution (0.1 M), extrapolation of the linear region to the potential axis gives a flat band potential of −0.41 V SCE , a holes density of 1.75 × 10 19 cm −3 and a space-charge region of 18 nm. The electrochemical impedance spectroscopy, measured over the frequency range (1 mHz–10 5 Hz), reveals the predominance of the bulk contribution with a constant phase element. The energy diagram shows the feasibility of La 2 CuO 4 for the H 2 evolution under visible light. The best performance occurs at pH 12.5 in the presence of S 2 O 3 2 − as holes scavenger. A liberation rate of 20.6 μmol mn −1 (g catalyst) −1 is obtained under full light (29 mW cm −2 ).