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 Cu2O facets {111} (octahedral) and {110} (rhombododecahedral) present a higher photo(electro)catalytic activity towards CO2RRs (CO2 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 Cu2O 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 Cu2O 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 Cu2O converts CO2 and H2O into methanol, while Cw-grown Cu2O produces ethanol. The different behaviour is related to the different Cu-Cu distance (the active catalytic centres) in the two facets.