Tuning *OH Oxidativity via a Cu-Co(OH)₂ Cocatalyst on a Hematite Photoanode for Selective Cyclohexanone Oxidation

Area of Science:

• Materials Science
• Electrochemistry
• Sustainable Chemistry

Background:

• Photoelectrochemical (PEC) synthesis offers a sustainable pathway for producing adipic acid (AA) from cyclohexanone.
• The efficiency of this process is limited by sluggish kinetics in the multielectron-transfer reactions.

Purpose of the Study:

• To develop a strategy for tuning the oxidativity of surface-adsorbed hydroxyl species (*OH) for selective AA synthesis.
• To improve the efficiency of PEC synthesis of adipic acid.

Main Methods:

• Integration of a Cu-doped cobalt hydroxide (Cu-Co(OH)₂) cocatalyst onto a hematite-based photoanode.
• Characterization of the photoanode's performance in terms of adipic acid productivity and Faradaic efficiency.
• Mechanistic studies to understand the role of copper in modulating the electronic properties of cobalt sites.

Main Results:

• The engineered photoanode achieved an adipic acid productivity of 10.4 μmol cm^-2 h^-1.
• A high Faradaic efficiency of 88.7% was obtained at 1.2 V vs RHE.
• Copper doping was found to induce electron-deficient characteristics at cobalt sites, enhancing the electrophilicity and oxidative capacity of *OH.

Conclusions:

• The electronic modulation of cocatalysts is a feasible strategy to tailor the oxidative capacity of active species in PEC systems.
• This approach provides new insights for designing advanced PEC systems for synthesizing value-added chemicals like adipic acid.
• The developed Cu-Co(OH)₂/hematite photoanode demonstrates significant potential for efficient and selective PEC synthesis of adipic acid.