Layered double hydroxide(LDH)-based materials:A mini-review on strategies to improve the performance for photocatalytic water splitting

The high energy demand we currently face in society and the subsequent large consumption of fossil fuels cause its depletion and increase the pollution levels.The quest for the production of clean energy from renewable and sustainable sources remains open.The conversion of solar energy into hydrogen via the water-splitting process,assisted by pho tores pons ive semiconductor catalysts,is one of the most promising technologies.Significant progress has been made on water splitting in the past few years and a variety of photocatalysts active not only under ultra-violet(UV) light but especially with the visible part of the electromagnetic spectrum have been developed.Layered double hydroxides(LDH)-based materials have emerged as a promising class of nanomaterials for solar energy applications owing to their unique layered structure,compositional flexibility,tunable bandgaps,ease of synthesis and low manufacturing costs.This review covers the most recent research dedicated to LDH materials for photocatalytic water-splitting applications and encompasses a range of synthetic strategies and post-modifications used to enhance their performance.Moreover,we provide a thorough discussion of the experimental conditions crucial to obtaining improved photoactivity and highlight the impact of some specific parameters,namely,catalysts loading,cocatalysts,sacrificial agents,and irradiation sources.This review provides the necessary tools to select the election technique for adequately enhancing the photoactivity of LDH and modified LDH-based materials and concludes with a critical summary that outlines further research directions.

Oxypropylation of Brazilian Pine-Fruit Shell Evaluated by Principal Component Analysis

Pine-fruit shell (PFS) is a lignocellulosic residue derived from the fruit of Araucaria angustifolia, a coniferoustree native of South America, part of a whole vegetation of the Atlantic Forest, found in the South and Southwestof Brazil. In this work PFS will be characterized and used in the production of PFS-based polyols throughoxypropylation. Three series were chosen (PFS/propylene oxide (PO) (w/v, g/mL) of 30/70, 20/80 and 10/90)with four catalyst levels (5%, 10%, 15% and 20%, (w/w, PFS based)). Oxypropylation occurred at moderateconditions of temperature, pressure and time giving rise to liquid polyols with a homopolymer content (PPO)ranging from 4-65%, a hydroxyl number (IOH) between 257-605 mg KOH/g and viscosities (V) varying from0.76 Pa.s to 373.90 Pa.s (20°C) for the series 20/80 and 10/90, while for the series 30/70, the viscosity reachedvalues higher than 500 Pa.s, 20°C. The unreacted PFS (UR) varied between 3.6% and 77.4% (PFS-basis). Afterthe PFS-based polyols production and characterization, a principal component analysis (PCA) was performed inorder to evaluate the established interactions between the used formulation variables and the obtained polyolproperties. The PCA analysis allowed to clarify the interactions between PFS and PO contents and the finalbiopolyol properties (PPO, IOH, V and UR). This approach showed to be a simple method to rationally analyzethe influence of the input formulation variables on the final polyol properties.