Orientational-growth of Cu2O {111} or {110} facets induced by frustules for CO2-H2O specific photo(electro)chemical conversion into methanol/ethanol under visible-light

p-Type-semiconductor Cu 2 O facets {111} ( octahedral ) and {110} ( rhombododecahedral ) present a higher photo(electro)catalytic activity towards CO2RRs (CO 2 Reduction Reaction) than {100} (cubic). Two frustules (the siliceous skeleton of microalgae Diatoms ) having a different morphology, namely: Navicula sp. ( Nsp , elongated pore-shape) and Conticribra weissflogii ( Cw , round pore-shape) have been used for the first time in this work as template for the orientational growth of Cu 2 O facets. Frustules are calcinated at 700 °C to avoid residual organics that may give false positives during photo(electro)catalysis. Each of the frustules is found to induce a facet of Cu 2 O preferentially. Nsp induces the {111} facet (Band-gap=2.26 eV), while Cw preferentially induces the {110} facet (Band-gap=1.96 eV). Under visible light irradiation, Nsp -grown Cu 2 O converts CO 2 and H 2 O into methanol, while Cw -grown Cu 2 O produces ethanol. The different behaviour is related to the different Cu-Cu distance (the active catalytic centres) in the two facets. Orientational growth of Cu 2 O {111} and {110} facets induced by Frustules and their activity as photo(electro)catalysts for the co-processing of CO 2 &H 2 O to energy products under visible-light irradiation. Two frustules, the siliceous skeleton of microalgae diatoms, with different morphology, Navicula sp. ( Nsp , elongated pores-shape) and Conticribra weissflogii ( Cw , round pores) are used for the orientational growth of Cu 2 O. Each of the frustules has found to induce a facet of Cu 2 O preferentially: Nsp induces the {111} facet, while Cw induces the {110} facet, which afford methanol and ethanol as CO2RPs in photo(electro)chemical reduction in water. • The first utilization of bio-silicates (frustules) as a template for Cu 2 O facets constructions. • Demonstration that different geometries of frustules produce different facets. • Utilization of facets in CO 2 reduction reactions. • Correlation of the Cu-Cu distance in facets to the product of CO 2 reduction. • Selective production of methanol or ethanol.