Atomic-scale interface engineering in Bi/Bi₂O₃ heterojunctions for selective CO₂ photoreduction to methanol

Area of Science:

• Materials Science
• Catalysis
• Photochemistry

Background:

• Efficient conversion of carbon dioxide (CO2) to valuable chemicals like methanol (CH3OH) is crucial for sustainable energy solutions.
• Metal-semiconductor heterojunctions offer potential for enhanced photocatalysis but often suffer from charge recombination and inefficient interfacial charge transfer.

Purpose of the Study:

• To strategically engineer an Ohmic junction at the bismuth (Bi)/bismuth oxide (Bi2O3) interface to enhance photocatalytic CO2-to-methanol conversion.
• To elucidate the mechanisms by which the Ohmic junction modulates charge behavior and interfacial energy for improved catalytic performance.

Main Methods:

• Fabrication of a Bi/Bi2O3 (BBO) Ohmic junction utilizing the local surface plasmon resonance effect.
• Employing theoretical calculations (e.g., DFT) and experimental characterization to analyze charge transfer dynamics and interfacial properties.
• Quantifying methanol production rates under light irradiation.

Main Results:

• The engineered Ohmic junction facilitates unidirectional electron transfer from Bi2O3 to Bi, suppressing charge recombination via a built-in electric field.
• Interfacial Bi sites preferentially adsorb and activate CO2 to form *COOH, with subsequent protonation occurring on metallic Bi sites.
• Reduced activation energy for the rate-limiting *CO2 → *COOH step by 0.6 eV.
• Achieved a methanol production rate of 610 μmol g-1 under light irradiation.

Conclusions:

• Ohmic junctions can simultaneously address bulk charge transport limitations and tailor surface catalytic activity in metal-semiconductor photocatalysts.
• The Bi/Bi2O3 Ohmic junction provides a universal design paradigm for developing efficient heterojunction photocatalysts for CO2 conversion.