Photon Up-Conversion with Lanthanide-Doped Oxide Particles for Solar H₂ Generation

Up-conversion (UC) of infrared (IR) photons into visible radiation constitutes a promising strategy to enhance the light harvesting efficiency of photovoltaic and photoelectrochemical devices. In the present study, we integrate Er³⁺/Yb³⁺-codoped yttrium oxide (Y₂O₃) submicrometric particles with outstanding up-conversion properties into mesoporous titanium oxide (TiO₂) structures sensitized with cadmium selenide (CdSe) for solar hydrogen generation. We demonstrate that the incorporation of these up-converting particles (UCP) leads to effective H₂ generation with IR photons. Moreover, based on the analysis of the emission lifetimes, we show that the optical interaction between the emitting UCPs and the CdSe absorber occurs via a radiative emission–reabsorption process. The low cost and toxicity and excellent chemical and thermal stability of our UC phosphors allow envisaging them as real candidates for the new generation of long-term photoelectrochemical devices for solar H₂ generation

Nickel-Doped Sodium Cobaltite 2D Nanomaterials: Synthesis and Electrocatalytic Properties

In this work we report a synthetic pathway to two-dimensional nanostructures of high oxidation state lamellar cobalt oxides with thicknesses of only few atom layers, through the combined use of precipitation in basic water at room temperature and gentle solid state topotactic transformation at 120 °C. The 2D nanomaterials are characterized by X-ray diffraction, nitrogen porosimetry, scanning electron microscopy, transmission electron microscopy and especially scanning transmission electron microscopy coupled to energy dispersive X-ray analysis and electron energy loss spectroscopy to assess the composition of the nanosheets and the oxidation state of the transition metal species. We show that the nanosheets preserve high oxidation states Co³⁺ and Co⁴⁺ of high interest for electrocatalysis of the oxygen evolution reaction (OER). By combining high Co oxidation state, surface-to-volume ratio and optimized nickel substitution, the 2D nanomaterials produced in a simple way exhibit high OER electrocatalytic activity and stability in alkaline aqueous electrolyte comparable to standard materials obtained in harsh thermal conditions