Enhanced hydrogen production from Al-water reaction: Strategies, performances, mechanisms and applications

Alongside the development of small-sized fuel cells, in situ hydrogen production technologies are essential to enable a compact, reliable and stable fuel supply. Among these technologies, Al-water reaction has tremendous potential and broad market prospect due to its low price, high gravimetric hydrogen storage density, environmentally benign byproducts and convenient storage and transportation. However, there is a passive oxide film on Al surface, hindering the direct reaction of Al with water, which has captured a surge of interest in enhancing the hydrogen production performance of Al-water reaction. In this review, the research progress in Al-water reaction is summarized. First, the physicochemical processes and related influencing factors of Al-water reaction are presented. Second, the strategies for enhancing Al-water reaction are critically discussed from five points of view: addition of alkalis, addition of catalysts, Al alloys, mechanical ball milling and surface modification. After that, the feasibility of hydrogen production from Al scraps is evaluated, and the potential applications of Al-water reaction are mapped. Finally, the challenges and opportunities of Al-hydrogen technology for fuel cell applications are outlined.