Structural diversity and hydrogen storage properties in the system K-Si-H

Area of Science:

• Materials Science
• Solid-State Chemistry
• Computational Materials Science

Background:

• Complex hydrides are actively researched for hydrogen storage applications.
• The K-Si-H system shows potential for novel hydrogen storage materials.
• KSiH3 demonstrates experimental hydrogen storage capacity and reversibility.

Purpose of the Study:

• To explore new phases within the K-Si-H system for hydrogen storage.
• To identify materials with high hydrogen content and density.
• To evaluate the thermodynamic stability and dehydrogenation properties of novel hydrides.

Main Methods:

• First-principles structure searches were employed to predict stable phases.
• Density Functional Theory (DFT) calculations were used to determine material properties.
• Thermodynamic stability and dehydrogenation temperatures were computationally evaluated.

Main Results:

• Two new, denser phases of K2SiH6 (space groups P3̄m1 and P6₃mc) were discovered at ambient pressure.
• The P3̄m1-K2SiH6 phase exhibits a high hydrogen content of 5.4 wt% and volumetric density of 88.3 g L⁻¹.
• Calculated dehydrogenation temperature for P3̄m1-K2SiH6 is favorable (-20.1/55.8 °C), decomposing into KSi + K + H₂.
• Three additional potential high-pressure hydrogen storage materials (K₂SiH₈, KSiH₇, KSiH₈) were identified.

Conclusions:

• K2SiH6, particularly the P3̄m1 phase, is a promising candidate for hydrogen storage due to its high hydrogen density and suitable dehydrogenation temperature.
• The findings provide valuable guidance for experimental synthesis and characterization of these novel complex hydrides.
• Further investigation into ternary hydrides under high pressure is warranted for discovering advanced hydrogen storage solutions.