Boron-nitrogen-hydrogen compounds represent a promising class of chemical hydrides for hydrogen storage, offering tunable properties and potential integration into decarbonization strategies. These materials, often referred to as B-N-H systems, exhibit a range of hydrogen release mechanisms, catalytic interactions, and synthesis pathways that make them candidates for advanced storage solutions. Their development aligns with the broader effort to identify efficient, safe, and scalable hydrogen carriers capable of supporting clean energy transitions.

One of the defining features of B-N-H systems is their ability to modulate hydrogen release temperatures through compositional and structural adjustments. For example, ammonia borane (NH3BH3) has been extensively studied due to its high gravimetric hydrogen capacity, approximately 19.6 wt%. Hydrogen release from ammonia borane occurs in multiple steps, beginning around 100°C with the liberation of one equivalent of H2, followed by subsequent releases at higher temperatures. However, uncontrolled decomposition can lead to the formation of volatile byproducts such as borazine and ammonia, which complicate the storage process and pose contamination risks. Modifying the B-N-H framework through chemical substitution or nanoconfinement can suppress unwanted byproducts and lower the effective dehydrogenation temperature. Incorporating metals like nickel or palladium as catalysts has been shown to enhance hydrogen release kinetics, with some systems achieving near-complete dehydrogenation below 150°C.

The synthesis of B-N-H compounds often involves complex routes that require precise control over reaction conditions. Ammonia borane, for instance, is typically produced through the reaction of ammonia with borane complexes in solvent-based systems, necessitating careful handling due to the reactivity of intermediates. Alternative pathways, such as mechanochemical synthesis or solvent-free methods, are being explored to improve scalability and reduce energy inputs. Despite these advances, challenges remain in minimizing side reactions that compete with hydrogen release. The formation of ammonia during decomposition is a significant concern, as it can poison fuel cell catalysts and reduce system efficiency. Strategies to mitigate this include the development of B-N-H variants with stronger B-N bonds or the use of scavengers to capture ammonia in situ.

A notable advantage of B-N-H systems is their compatibility with hybrid storage approaches. Combining these chemical hydrides with physical storage methods, such as porous adsorbents or metal-organic frameworks (MOFs), can enhance overall performance. For example, dispersing ammonia borane within a MOF matrix has been demonstrated to reduce decomposition temperatures and improve reversibility. Similarly, coupling B-N-H compounds with liquid organic hydrogen carriers (LOHCs) could enable denser storage formats while leveraging existing infrastructure for transport and distribution. These hybrid systems aim to balance high hydrogen capacity with manageable release kinetics, addressing one of the critical bottlenecks in hydrogen storage technology.

The role of B-N-H compounds in decarbonization efforts hinges on their lifecycle emissions and integration with renewable energy sources. While ammonia borane and related materials can store hydrogen produced via electrolysis using renewable electricity, the energy intensity of their synthesis and regeneration must be considered. Current regeneration methods often require high-pressure hydrogenation steps or chemical reductants, which may offset some environmental benefits. Research is ongoing to develop low-energy regeneration pathways, such as electrochemical or photochemical approaches, that could align these materials with net-zero objectives.

In industrial applications, B-N-H systems face competition from established storage technologies like compressed gas and metal hydrides. Their adoption will depend on achieving competitive volumetric and gravimetric densities while maintaining safety and cost-effectiveness. Pilot-scale demonstrations have shown promise, particularly in niche applications where controlled hydrogen release and moderate temperatures are advantageous. For instance, ammonia borane derivatives have been tested in portable power units and backup energy systems, where their solid-state storage and stability under ambient conditions are beneficial.

Material stability under repeated cycling remains a critical challenge for B-N-H compounds. Many systems suffer from gradual capacity loss due to incomplete rehydrogenation or the accumulation of decomposition byproducts. Advances in catalyst design and the exploration of new B-N-H compositions, such as diammoniate of diborane or polyborazylene, aim to improve cyclability. The latter has shown potential for reversible hydrogen storage with reduced ammonia emission, though long-term durability data are still limited.

From a safety perspective, B-N-H compounds generally exhibit lower flammability risks compared to gaseous or liquid hydrogen, but they require careful handling to prevent exposure to moisture or heat during storage. The development of stabilized formulations, including polymer-coated or pelletized forms, has improved their practicality for real-world use. Standardization efforts are also underway to establish protocols for large-scale handling and transportation, ensuring compatibility with existing safety frameworks.

The future trajectory of B-N-H systems will likely involve their integration into multifunctional energy platforms. For example, coupling these materials with fuel cells or combustion turbines could enable efficient power generation with on-demand hydrogen release. Additionally, their use in sector-coupling applications, such as providing hydrogen for industrial heating or chemical synthesis, could further drive adoption. As research progresses, the scalability of production and regeneration processes will be a decisive factor in determining their role in the hydrogen economy.

In summary, boron-nitrogen-hydrogen compounds offer a versatile and tunable platform for hydrogen storage, with ongoing advancements addressing challenges in synthesis, decomposition control, and system integration. Their development reflects a broader push toward materials-based solutions that can meet the demands of diverse applications while supporting global decarbonization goals. Continued innovation in catalysis, hybrid systems, and lifecycle management will be essential to unlocking their full potential in the evolving energy landscape.