Steric effects in the hydrogen evolution reaction based on the TMX₄ active center: Fe-BHT as a case study

Area of Science:

• Materials Science
• Catalysis
• Computational Chemistry

Background:

• The hydrogen evolution reaction (HER) is crucial for sustainable energy technologies.
• Developing efficient and cost-effective catalysts for HER is a significant challenge.
• Transition metal-based compounds are actively investigated as potential HER catalysts.

Purpose of the Study:

• To identify the most efficient transition metal-boron-doped fullerene-like structure (TM-BHT) catalyst for HER.
• To elucidate the electronic structure and bonding mechanisms governing HER activity in Fe-BHTs.
• To explore novel descriptors for HER activity, including steric effects and point group symmetry.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to investigate a series of TM-BHTs (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni).
• Analysis of electronic structure, including orbital participation and hydrogen adsorption states.
• Introduction and validation of a steric effect descriptor and strain engineering techniques.

Main Results:

• Fe-BHT was identified as the most active catalyst, exhibiting an exceptionally low overpotential of 0.09 V for HER.
• The Fe d-orbitals were found to be crucial for hydrogen adsorption rather than direct bonding with the active center's S/N atoms.
• A novel descriptor, the energy gap influenced by steric effects, was correlated with HER activity.
• Strain engineering confirmed the significance of steric effects and highlighted the role of point group symmetry.

Conclusions:

• Fe-BHT emerges as a highly promising catalyst for the hydrogen evolution reaction.
• Steric effects and point group symmetry are identified as critical, previously overlooked factors influencing HER catalytic activity.
• The findings provide new insights for the rational design of advanced HER electrocatalysts.