A review on effect of synthesis conditions on the formation of layered double hydroxides

Highlights: • The LDHs are known as hydrotalcite-like compounds. • The conventional synthesis method of LDH materials is co-precipitation method. • Synthesis conditions can influence on the hydrotalcite formation. -- Abstract: The most common method for the synthesis of layered double hydroxides (LDHs) is co-precipitation. This review is focused on the summarizing of results concerning the influence of synthesis conditions on the formation of layered double hydroxides. Mainly, the review considers synthesis of ZnAl-LDHs, CuAl-LDHs due to a lack of information about the aforementioned materials and wide literature information about MgAl-LDHs, which is the most common to be used as a support for catalysts. CuAl-LDHs and ZnAl-LDHs can be applied as the catalysts in a variety of reactions such as methanol synthesis, methanol steam reforming, reductive amination, etc., or efficient photocatalysts for removing organic dye molecules. It is important to investigate the synthesis conditions under which CuAl-LDHs form, as they can affect catalytic performance in the aforementioned reactions. The effect of pH is considered in this review since LDH for different metal salts can be formed at different pH. The concentration of base solution during precipitation and the nature of base solution can also affect the hydrotalcite formation. Data concerning the metal precursors used and their concentrations are also included in this review.