Controlling Hydrogen Evolution and CO₂ Reduction at Transition Metal Hydrides.

Area of Science:

• Catalysis and Electrochemistry
• Materials Science
• Sustainable Chemistry

Background:

• Fuel-forming reactions like hydrogen evolution (HER) and CO2 reduction (CO2R) are crucial for a carbon-neutral economy.
• Metal hydride intermediates play a key role in these catalytic and electrocatalytic processes.
• Controlling metal hydride reactivity is essential for developing selective, fast, and low-overpotential redox reactions.

Purpose of the Study:

• To understand the kinetic and thermodynamic aspects of metal hydride reactivity for designing advanced electrocatalysts.
• To investigate free energy changes and reaction rates of catalytic steps by synthesizing and studying proposed intermediates.
• To guide the design of electrocatalysts for selective CO2 reduction to formate and efficient hydrogen evolution.

Main Methods:

• Studied solvent-dependent changes in hydricity for transition metal hydrides.
• Applied hydricity values to optimize HER and CO2R catalysis, providing guidelines for selective CO2 reduction.
• Investigated kinetic information of catalytic cycles to identify rate-determining steps and explored catalyst design strategies (electrostatic and steric) to inhibit HER.

Main Results:

• Developed a framework using hydricity to achieve selective CO2 reduction to formate without H2 generation.
• Designed an electrocatalyst for CO2 and formate interconversion at low overpotentials.
• Explored bioinspired approaches, mimicking formate dehydrogenase, for generating hydride donors at milder potentials.

Conclusions:

• Hydricity is a key parameter for designing selective and efficient electrocatalysts for fuel-forming reactions.
• Strategies involving electrostatic and steric interactions can kinetically inhibit unwanted HER.
• Bioinspired hydride transfer offers a promising new direction for catalysis under mild conditions.