Influence of morphology and composition of spherical layered double hydroxide particles and derived mixed oxides on photocatalytic CO 2 reduction

Abstract

[EN] Considering the flexibility in the synthesis that allows the formation of materials with more than two metals, the present study reports the preparation of trimetallic layered double hydroxides (LDHs) having Al as structural tripositive cation, Ti as photocatalytically active d 0 transition metal and either Ni or Co as dipositive cation. In addition, these LDHs were used as precursors of the corresponding trimetallic mixed oxides (MO). LDH and MO materials in combination with Ru(bpy) 3 Cl 2 as photosensitizer and triethanolamine as sacrificial electron donor were used as catalysts for CO 2 reduction under solar light irradiation. A different product selectivity, either CH 4 for Ni-LDH or CO and H 2 for Co -MO, was observed with production rates for CH 4 or CO that are among the highest reported for these systems. The role of the inorganic materials in the photocatalytic process was supported by transient absorption spectroscopy that revealed the quenching of the Ru(bpy) 3 Cl 2 triplet excited state by Ni-LDH or Co -MO. An important finding was that the trimetallic Co -Ti -Al oxide with cobaltite structure is able to perform CO 2 reduction in spite that the reduction potential of its conduction band is not sufficient to perform the process, evidence by photoluminescence revealing the existence of an upper electronic state responsible for the reduction. These results show the interest in screening multimetallic materials in photocatalysis due to their improved performance and diverse properties.