The present study reports on the synthesis and the electrochemical behavior of Na_0.71CoO₂, a promising candidate as cathode for Na-based batteries. The material was obtained in two different morphologies by a double-step route, which is cheap and easy to scale up: the hydrothermal synthesis to produce Co₃O₄ with tailored and nanometric morphology, followed by the solid-state reaction with NaOH, or alternatively with Na₂CO₃, to promote Na intercalation. Both products are highly crystalline and have the P2-Na_0.71CoO₂ crystal phase, but differ in the respective morphologies. The material obtained from Na₂CO₃ have a narrow particle length (edge to edge) distribution and 2D platelet morphology, while those from NaOH exhibit large microcrystals, irregular in shape, with broad particle length distribution and undefined exposed surfaces. Electrochemical analysis shows the good performances of these materials as a positive electrode for Na-ion half cells. In particular, Na_0.71CoO₂ thin microplatelets exhibit the best behavior with stable discharge specific capacities of 120 and 80 mAh g⁻¹ at 5 and 40 mA g⁻¹, respectively, in the range 2.0–3.9 V vs. Na⁺/Na. These outstanding properties make this material a promising candidate to construct viable and high-performance Na-based batteries.

Chitosan is a marine-origin polysaccharide obtained from the deacetylation of chitin, the main component of crustaceans’ exoskeleton, and the second most abundant in nature. Although this biopolymer has received limited attention for several decades right after its discovery, since the new millennium chitosan has emerged owing to its physicochemical, structural and biological properties, multifunctionalities and applications in several sectors. This review aims at providing an overview of chitosan properties, chemical functionalization, and the innovative biomaterials obtained thereof. Firstly, the chemical functionalization of chitosan backbone in the amino and hydroxyl groups will be addressed. Then, the review will focus on the bottom-up strategies to process a wide array of chitosan-based biomaterials. In particular, the preparation of chitosan-based hydrogels, organic–inorganic hybrids, layer-by-layer assemblies, (bio)inks and their use in the biomedical field will be covered aiming to elucidate and inspire the community to keep on exploring the unique features and properties imparted by chitosan to develop advanced biomedical devices. Given the wide body of literature that has appeared in past years, this review is far from being exhaustive. Selected works in the last 10 years will be considered.

The present study reports on a simple preparation strategy of a hybrid catalyst, TiO₂/HKUST-1, containing TiO₂ anatase nanoparticles (NPs) with tailored morphology and photocatalytic activity coupled with a porous metal-organic framework (MOF), namely HKUST-1, as an advanced material for the CO₂ photocatalytic reduction. In detail, TiO₂/HKUST-1 catalyst was prepared via an easy slow-diffusion method combined with a step-by-step self-assembly at room temperature. The growth of crystalline HKUST-1 onto titania surface was achieved by functionalizing TiO₂ nanocrystals, with phosphoesanoic acid (PHA), namely TiO₂-PHA, which provides an intimate contact between MOF and TiO₂. The presence of a crystalline and porous shell of HKUST-1 on the TiO₂ surfaces was assessed by a combination of analytical and spectroscopic techniques. TiO₂/HKUST-1 nanocomposite showed a significant efficiency in reducing CO₂ to CH₄ under solar light irradiation, much higher than those of the single components. The role of MOF to improve the photoreduction process under visible light was evidenced and attributed either to the relevant amount of CO₂ captured into the HKUST-1 porous architecture or to the hybrid structure of the material, which affords enhanced visible light absorption and allows an effective electron injection from TiO₂-PHA to HKUST-1, responsible for the photochemical reduction of CO₂.