Synergistic Dual-Channel Charge Separation in Cr-TiO_2-x for Solar H₂O₂ Synthesis

Area of Science:

• Materials Science
• Photocatalysis
• Sustainable Chemistry

Background:

• Current solar hydrogen peroxide (H2O2) synthesis methods are limited by inefficient charge carrier utilization.
• The anthraquinone process for H2O2 production is energy-intensive and unsustainable.

Purpose of the Study:

• To develop a novel photocatalyst for efficient and sustainable solar-driven H2O2 synthesis.
• To enable simultaneous and synergistic harnessing of photogenerated electrons and holes for H2O2 production.

Main Methods:

• Fabrication of ultrathin TiO2 nanosheets decorated with atomic chromium (Cr) and oxygen vacancies (OVs) (Cr-TiO2-x).
• Utilized in situ X-ray absorption/emission spectroscopy and excited-state density functional theory (DFT) calculations.
• Investigated the cooperative coupling of two-electron water oxidation (2e- WOR) and two-electron oxygen reduction (2e- ORR).

Main Results:

• Achieved a record H2O2 production rate of 764.9 µmol g-1 h-1 in pure water without sacrificial agents.
• Demonstrated a solar-to-chemical conversion efficiency of 1.23% and an apparent quantum yield of 11.5% at 420 nm.
• Cr single atoms facilitated hole accumulation for 2e- WOR, while OVs trapped electrons for 2e- ORR, suppressing charge recombination via a proton-coupled electron transfer (PCET) loop.

Conclusions:

• The Cr-TiO2-x photocatalyst enables efficient H2O2 synthesis through a dual-redox mechanism with spatially separated active sites.
• Established a blueprint for atomic-level design of dual-redox photocatalysts for solar fuel applications.
• Provided direct spectroscopic evidence of excited-state charge partitioning for enhanced photocatalysis.