Solar Hydrogen Production and Storage in Solid Form: Prospects for Materials and Methods.

Climatic changes are reaching alarming levels globally, seriously impacting the environment. To address this environmental crisis and achieve carbon neutrality, transitioning to hydrogen energy is crucial. Hydrogen is a clean energy source that produces no carbon emissions, making it essential in the technological era for meeting energy needs while reducing environmental pollution. Abundant in nature as water and hydrocarbons, hydrogen must be converted into a usable form for practical applications. Various techniques are employed to generate hydrogen from water, with solar hydrogen production-using solar light to split water-standing out as a cost-effective and environmentally friendly approach. However, the widespread adoption of hydrogen energy is challenged by transportation and storage issues, as it requires compressed and liquefied gas storage tanks. Solid hydrogen storage offers a promising solution, providing an effective and low-cost method for storing and releasing hydrogen. Solar hydrogen generation by water splitting is more efficient than other methods, as it uses self-generated power. Similarly, solid storage of hydrogen is also attractive in many ways, including efficiency and cost-effectiveness. This can be achieved through chemical adsorption in materials such as hydrides and other forms. These methods seem to be costly initially, but once the materials and methods are established, they will become more attractive considering rising fuel prices, depletion of fossil fuel resources, and advancements in science and technology. Solid oxide fuel cells (SOFCs) are highly efficient for converting hydrogen into electrical energy, producing clean electricity with no emissions. If proper materials and methods are established for solar hydrogen generation and solid hydrogen storage under ambient conditions, solar light used for hydrogen generation and utilization via solid oxide fuel cells (SOFCs) will be an efficient, safe, and cost-effective technique. With the ongoing development in materials for solar hydrogen generation and solid storage techniques, this method is expected to soon become more feasible and cost-effective. This review comprehensively consolidates research on solar hydrogen generation and solid hydrogen storage, focusing on global standards such as 6.5 wt% gravimetric capacity at temperatures between -40 and 60 °C. It summarizes various materials used for efficient hydrogen generation through water splitting and solid storage, and discusses current challenges in hydrogen generation and storage. This includes material selection, and the structural and chemical modifications needed for optimal performance and potential applications.