H2 evolution by water SPLITTING on Rh/La2O3

Abstract

The physicochemical and electrochemical properties of rhodium catalysts supported on La2O3 denoted XRhLa (X = 1 and 5% wt. Rh) prepared by impregnation using RhCl6H2O as precursor salt were studied. The solids were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal analysis (TG/TDA) and hydrogen chemisorption (HC) to evaluate the dispersion of the metal phase. The temperature-programmed reaction with hydrogen (H2-TPR), carbon monoxide (CO-TPR) or methane (CH4-TPR) were carried out to elucidate there effects on catalytic reaction. The adsorption and decomposition of H2O has been investigated on the surface catalysts. The number of reduced centers of lanthanum in Rh/La2O3 catalysts was measured by in situ oxidation of these centers at oxydation temperature of water (TOXtov) by water pulses according to the following reaction (Reduced centers + H2O→Oxidized center + H2). The amount of hydrogen Q(H), evolved in the reaction allows us to calculate the number of reduced centers of the support since the Rh metal is not oxidized. The results showed that although the conversion rate of water to H2 is low, the 5% wt. Rh catalyst is a promising candidate in the water adsorption and dissociation compared to the 1% wt.