Competitive hydrogen evolution and multiple proton-coupled electron transfer reactions limit photoelectrochemical CO2 reduction in aqueous electrolyte. Here, oxygen-terminated lightly boron-doped diamond (BDDL) thin films were synthesized as a semiconductor electron source to accelerate CO2 reduction. However, BDDL alone could not stabilize the intermediates of CO2 reduction, yielding a negligible amount of reduction products. Silver nanoparticles were then deposited on BDDL because of their selective electrochemical CO2 reduction ability. Excellent selectivity (estimated CO:H2 mass ratio of 318:1) and recyclability (stable for five cycles of 3 h each) for photoelectrochemical CO2 reduction were obtained for the optimum silver nanoparticle-modified BDDL electrode at −1.1 V vs. RHE under 222-nm irradiation. The high efficiency and stability of this catalyst are ascribed to the in situ photoactivation of the BDDL surface during the photoelectrochemical reaction. The present work reveals the potential of BDDL as a high-energy electron source for use with co-catalysts in photochemical conversion.

In this work, we report a facile synthesis of Cu−SnOx hybrid nanostructures on lightly boron‐doped diamond (BDDL) electrodes by a potentiodynamic electrodeposition method. The deposition potential for Cu−SnOx hybrid nanostructures was cycled between 0 to −1.0 V vs Ag/AgCl for five consecutive runs at a scan rate of 50 mV/sec. The growth of the Cu−SnOx hybrid nanostructures on BDDL was optimized by varying the number of potentiodynamic deposition cycles and precursor concentration. A uniform particle size distribution of Cu−SnOx was obtained on BDDL using 10 mM CuSO4 and 5 mM SnCl2 in 50 mM aqueous NaNO3. Detail of surface morphology and surface elemental composition of the optimized Cu−SnOx hybrid nanostructures modified BDDL electrodes were characterized. The optimized Cu−SnOx hybrid nanostructures on BDDL were found to be in the size range of 50 to 100 nm with a 3 to 10 nm SnOx‐rich shell. This optimized Cu−SnOx modified BDDL electrode was tested for electrochemical CO2 reduction reaction in aqueous electrolyte and found to produce primarily CO with a Faradaic Efficiency of up to 82.5 % at −1.6 V vs Ag/AgCl.

A mesoporous TiO2/BDD hybrid electrode showed a synergetic effect between electrochemical water treatment and photocatalytic water treatment.

There is a need for highly efficient photocatalysts, particularly for water purification. In this study, we fabricated a mesoporous TiO2 thin film on a boron-doped diamond (BDD) layer by a surfactant-assisted sol-gel method, in which self-assembled amphiphilic surfactant micelles were used as an organic template. Scanning electron microscopy revealed uniform mesopores, approximately 20 nm in diameter, that were hexagonally packed in the TiO2 thin film. Wide-angle X-ray diffraction and Raman spectroscopy clarified that the framework crystallized in the anatase phase. Current–voltage (I–V) measurements showed rectification features at the TiO2/BDD heterojunction, confirming that a p–n hetero-interface formed. The as-synthesized mesoporous TiO2/BDD worked well as a photocatalyst, even with a small volume of TiO2 (15 mm × 15 mm × c.a. 1.5 µm in thickness). The use of deep UV light (λ = 222 nm) as a light source was necessary to enhance photocatalytic activity, due to photo-excitation occurring in both BDD and TiO2.