Review of photo- and electro-catalytic multi-metallic layered double hydroxides

The development of efficient photo/electrocatalysis using sustainable renewable resources to prepare high value-added products is now a major goal to achieve new environmentally friendly technologies. However, existing solutions still offer unsatisfied catalytic efficiency and low energy utilization. Therefore, it is paramount to develop new strategies to control the morphology and structure of functional materials to improve their photo/electrocatalytic activity. Layered double hydroxides (LDHs), as a kind of two-dimensional (2D) materials, have been largely explored in photo/electrocatalytic reactions due to their extensive tenability of elemental composition and interlayered anions. Furthermore, the intrinsic feature of atomic dispersion has been utilized to introduce more active sites to further improve the reaction performance. Herein, we review strategies that have been developed for introducing more active sites into or onto the LDH layer for the construction of multi-metallic LDHs based photo/electrocatalytic material. The accompanied structure and electronic changes that are pivotal for modulation for catalytic activity are proposed, such as, improving carrier transportation, and optimizing molecular activation energy. We review the catalytic performance of multi-metallic LDHs for photo/electrocatalytic water splitting, CO₂ photoreduction, CO hydrogenation, heavy metal mineralization/reutilization and beyond. We highlight future challenges and opportunities to design multi-metallic LDHs to address future photo/electrocatalysis research challenges.