Nanomaterials enhancing the solid-state storage and decomposition of ammonia

Abstract

Hydrogen is ideal for producing carbon-free and clean-green energy with which to save the world from climate change. Proton exchange membrane fuel cells use to hydrogen to produce 100% clean energy, with water the only by-product. Apart from generating electricity, hydrogen plays a crucial role in hydrogen-powered vehicles. Unfortunately, the practical uses of hydrogen energy face many technical and safety barriers. Research into hydrogen generation and storage and reversibility transportation are still in its very early stages. Ammonia (NH3) has several attractive attributes, with a high gravimetric hydrogen density of 17.8 wt.% and theoretical hydrogen conversion efficiency of 89.3%. Ammonia storage and transport are well-established technologies, making the decomposition of ammonia to hydrogen the safest and most carbon-free option for using hydrogen in various real-time applications. However, several key challenges must be addressed to ensure its feasibility. Current ammonia decomposition technologies require high temperatures, pressures and non-recyclable catalysts, and a sustainable decomposition mechanism is urgently needed. This review article comprehensively summarises current knowledge about and challenges facing solid-state storage of ammonia and decomposition. It provides potential strategic solutions for developing a scalable process with which to produce clean hydrogen by eliminating possible economic and technical barriers.

Recent progress on the synthesis and applications of high-entropy alloy catalysts

“…At present, HEAs-related catalytic reactions can be mainly divided into two categories, one is thermal-driven catalysis, which includes ammonia decomposition reactions, ethanol oxidation reactions, methanol oxidation reactions, CO oxidation reactions, and the other is electrocatalysis, which mainly includes hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO 2 RR) and so on [60]. Next, we will introduce the application of HEAs in these reactions in detail.…”

Recent Insights into Low-Surface-Area Catalysts for Hydrogen Production from Ammonia

“…Most of the investigations that aim to generate H 2 from NH 3 decomposition are performed at elevated temperatures [14,15,31]. However, the application of NH 3 as a hydrogen carrier requires in situ production at suitable reaction conditions (temperatures and pressures) to be used in fuel cells.…”

“…Therefore, a high surface area is usually thought to be a positive factor for dispersing metals, resulting in a larger number of active sites and assisting the mass transfer of the reaction [14,31,34,55,76,94]. In contrast, it is found that the utilization of precursors, mainly perovskites or hydrotalcites, could help to control the metal size to be small, providing high dispersion.…”