Hydride Shuttle Formation and Reaction with CO₂ on GaP(110)

Area of Science:

• Electrochemistry and Catalysis
• Materials Science
• Computational Chemistry

Background:

• Hydrogenated N-heterocycles, like pyridine (Py), are investigated as co-catalysts for CO2 reduction over semiconductor photoelectrodes.
• Initial hypotheses suggested dihydropyridine (DHP*) as the catalytic intermediate, but its formation via surface hydride transfer was kinetically hindered.
• An alternative intermediate, deprotonated dihydropyridine (2-PyH- *), was proposed due to favorable thermodynamic predictions for its formation.

Purpose of the Study:

• To investigate the catalytic mechanism of CO2 reduction using pyridine-based co-catalysts on semiconductor surfaces.
• To compare the catalytic activity and hydride donation ability of dihydropyridine (DHP*) and deprotonated dihydropyridine (2-PyH- *).
• To determine the energetic feasibility and kinetic viability of 2-PyH- * formation and its role in CO2 reduction on GaP photoelectrodes.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to study the energetics of intermediate formation and CO2 reduction.
• Thermodynamic favorability of 2-PyH- * formation was assessed on various semiconductor surfaces (GaP(111), CdTe(111), CuInS2(112)).
• Kinetic feasibility and reaction energetics were investigated on the GaP(110) surface under illumination.

Main Results:

• The formation of 2-PyH- * is thermodynamically favored on multiple semiconductor surfaces active for CO2 reduction.
• 2-PyH- * demonstrated superior hydride donating ability for CO2 reduction compared to DHP*.
• On illuminated GaP(110), 2-PyH- * formation is kinetically feasible, supporting its role as an effective catalytic intermediate.

Conclusions:

• The deprotonated dihydropyridine (2-PyH- *) is a more effective co-catalyst than dihydropyridine (DHP*) for CO2 reduction.
• The study supports the hypothesis that 2-PyH- * catalyzes CO2 reduction on p-GaP electrodes.
• Computational insights provide a mechanistic understanding for enhanced CO2 reduction efficiency using pyridine derivatives.