Hydrogen production on the new hetero-system Pr2NiO4/SnO2 under visible light irradiation

Abstract

The Pr2NiO4/SnO2 heterojunction with a mass ratio equal to unity was tested with success for the hydrogen production under visible light irradiation. Pr2NiO4, prepared by nitrate route, crystallizes in a tetragonal symmetry with K2NiF4 type structure. The physical, electrical and photo-electrochemical characterizations are correlated to show the feasibility of Pr2NiO4 for the hydrogen formation under visible light. The enhanced hydrogen production activity is due to electron injection of activated conduction band Pr2NiO4-CB (−1.53 VSCE) into SnO2-CB (−0.87 VSCE) which acts as an electron pump, resulting in better water reduction. The band gap of the semiconductor Pr2NiO4 is 1.81 eV with a direct optical transition. Pr2NiO4 acquired p type conductivity, due to oxygen insertion in the layered lattice with an activation energy of 0.09 eV. The flat band potential (Efb, 0.18 VSCE), very close to the photocurrent onset potential (0.13 VSCE) and the density of the holes (NA, 1.85 1020 cm−3) were obtained from the Mott-Schottky characteristic. H2 production rate of 24.3 μmol g−1 min−1 is obtained with a quantum yield of 1.45% within 30 min under optimal conditions (1 mg of catalyst/mL, pH ~12 and 50 °C) in presence of S2O2−3 as hole scavenger under visible light flux of 29 mW cm−2.