Question

Describe two ways hydrogen can be stored in compounds of boron.

Short answer

Hydrogen can be stored in borohydrides like sodium borohydride, or in ammonia borane.

Step-by-step solution

Discussing Borohydrides

One way to store hydrogen in compounds of boron is through borohydrides. These compounds, such as sodium borohydride (NaBH₄), can store large amounts of hydrogen. The hydrogen is chemically bonded within the compound and can be released when needed, often through reactions involving heat or catalysts.

Explaining Ammonia Borane

Another method of storing hydrogen is in ammonia borane (NH₃BH₃). This compound consists of ammonia and borane combined together, storing hydrogen in a solid state. Upon heating, the compound can decompose to release hydrogen gas, making it a useful storage medium.

Key concepts

Borohydrides

Borohydrides are a fascinating group of compounds that offer a practical method for hydrogen storage. These compounds, like sodium borohydride (NaBH₄), are known for their high hydrogen content. Borohydrides consist of metal cations and borohydride anions

• Sodium borohydride (NaBH₄) is one of the most studied and used borohydrides for hydrogen storage.
• It can store a significant amount of hydrogen, making it one of the highest capacity hydrogen storage materials.

This hydrogen is bonded chemically to the boron atom and can be released by breaking these chemical bonds

• Typically, hydrogen release is induced through heating or adding a catalyst.
• Once released, the hydrogen can be used for energy purposes, such as fueling a hydrogen cell.

The process of releasing hydrogen from borohydrides is mainly controlled and requires specific conditions to strike a balance between safety and efficiency.

Ammonia Borane

Ammonia borane (NH₃BH₃) is another significant compound utilized in hydrogen storage solutions. It combines ammonia (NH₃) and borane (BH₃), holding hydrogen primarily in a solid form. This solid-state storage is both stable and dense

• Ammonia borane contains a high percentage of hydrogen by weight, making it an attractive option for energy storage and transportation.
• Its solid form allows for convenient handling and storage, minimizing the risk of leakage or loss.

Upon heating, ammonia borane decomposes to release hydrogen gas

• This decomposition process is typically initiated at relatively low temperatures, which facilitates practical usage.
• The desirable aspect of ammonia borane is its ability to release hydrogen in a controlled manner.

Researchers continue to study the exact mechanisms and optimize the conditions under which hydrogen can be efficiently released from ammonia borane.

Chemical Bonding

Chemical bonding plays a crucial role in the context of hydrogen storage, particularly in boron compounds. The hydrogen storage capacity depends significantly on how hydrogen is bonded within a compound. There are several types of chemical bonds relevant to this field

• In borohydrides, hydrogen atoms are bonded to boron, typically forming covalent bonds.
• Covalent bonds involve the sharing of electrons, which provides stability and controls the release of hydrogen.
• Ammonia borane features a combination of covalent and dative bonds between hydrogen, boron, and nitrogen atoms.

The strength and stability of these bonds dictate how safely and efficiently hydrogen can be stored and later released

• For practical applications, innovations aim to manage these bonds to optimize both storage capacity and release kinetics.
• Understanding chemical bonding in these compounds aids in the development of advanced materials for hydrogen storage needs.

Hydrogen Release Mechanisms

The release of hydrogen from storage materials like borohydrides and ammonia borane is a key aspect of their utility. Hydrogen release mechanisms are intrinsic to the chemistry of these compounds, governed by various factors including temperature and catalysts.

• For borohydrides, hydrogen is typically released through thermal decomposition or catalytic processes that break the chemical bonds holding hydrogen.
• Ammonia borane releases hydrogen when heated, undergoing a controlled chemical reaction that liberates hydrogen gas.
• Using catalysts can enhance the release rates, offering more efficient and controlled hydrogen recovery.

Understanding and optimizing these mechanisms are crucial for deploying hydrogen storage technologies in real-world applications

• Research focuses on reducing the energy requirements for hydrogen release to improve practicality and cost-effectiveness.
• Innovations aim to develop new materials or processes that can enhance the efficiency of hydrogen release.

These efforts are geared towards making hydrogen storage more viable for a wide range of energy applications, particularly in clean energy and transportation.