**1. Introduction**

Catalysts are the most effective and economically feasible way to increase yield of the product(s) in various production processes. The catalysts prepared with innovative approaches could have novel catalytic properties such as increased number of active sites, highly selective to the target product, resistance to deactivation, and extended lifetime. The precious metal-based catalysts with these properties could provide significant economic benefits for the production of hydrogen which is currently expensive. The hydrothermal gasification technologies (sub- and supercritical water gasification and aqueous-phase reforming) have considerable economic, environmental, and technical advantages over other energy-extensive conversion

technologies [1]. These processes are compatible with water-soluble feedstocks such as biomass and gasification reactions that take place at lower temperatures. However, the absence of practical catalysts in hydrothermal conditions is a main challenge that impedes upscaling of these technologies for hydrogen gas production. Increasing demand, limited supply, and undesirable byproducts due to current methods indicate the need for the development of innovative, economically feasible, highly active, and stable catalysts for hydrothermal conversion of biomass-derived compounds to hydrogen in higher yield and richer composition.
