As a single atom Pd outperforms Pt as the most active co-catalyst for photocatalytic H₂ evolution

Area of Science:

• Materials Science
• Catalysis
• Nanotechnology

Background:

• Titanium dioxide (TiO2) is a benchmark photocatalyst for hydrogen generation.
• Noble metal nanoparticles are commonly used co-catalysts, but their single-atom counterparts are less explored.
• Controlling co-catalyst structure at the atomic level is crucial for optimizing photocatalytic performance.

Purpose of the Study:

• To investigate the photocatalytic activity of single-atom (SA) noble metal co-catalysts (Pd, Pt, Au) on TiO2 nanosheets.
• To compare the performance of SAs with traditional nanoparticle co-catalysts for hydrogen evolution.
• To elucidate the structure-activity relationship governing SA co-catalyst performance.

Main Methods:

• Synthesized anatase TiO2 nanosheets with controlled surface vacancies (Ti3+-Ov) via thermal reduction.
• Anchored identical loadings of single atoms of Palladium (Pd), Platinum (Pt), and Gold (Au) onto the TiO2 surface.
• Measured photocatalytic hydrogen (H2) generation rates and performed density functional theory (DFT) calculations.

Main Results:

• Single-atom Pd exhibited significantly higher H2 generation activity compared to single-atom Pt and Au.
• The activity sequence for single-atom co-catalysts (Pd >> Pt > Au) differs markedly from the nanoparticle sequence (Pt > Pd > Au).
• DFT calculations suggest charge localization on the noble metal SAs influences their catalytic activity.

Conclusions:

• Single-atom noble metals, particularly Pd, offer a promising avenue for enhancing photocatalytic hydrogen production.
• The unusual activity sequence highlights the importance of atomic dispersion and electronic interactions between co-catalysts and supports.
• Tailoring surface defects and co-catalyst structure at the atomic level is key to designing efficient photocatalysts.