Solely light-induced water splitting represents a promising avenue for a carbon-free energy future, based on reliable energy sources. Such processes can be performed using coupled semiconductor materials (the so-called direct Z-scheme design) that facilitate spatial separation of (photo)excited electrons and holes, prevent their recombination, and allow water-splitting half-reactions proceeding at each corresponding semiconductor side. In this work, we proposed and prepared a specific structure, based on WO3g-x/CdWO4/CdS coupled semiconductors, created by annealing of a common WO3/CdS direct Z-scheme. WO3-x/CdWO4/CdS flakes were further combined with a plasmon-active grating for the creation of the so-called artificial leaf design, making possible complete utilization of the sunlight spectrum. The proposed structure enables water splitting with high production of stoichiometric amounts of oxygen and hydrogen without undesirable catalyst photodegradation. Several control experiments confirm the creation of electrons and holes participating in the water splitting half-reaction in a spatially selective manner.

• Klíčová slova
• Z-scheme, artificial leaf, overall water splitting, plasmon photosensitization, sunlight,
• Publikační typ
• časopisecké články MeSH

Color centers in diamond have shown excellent potential for applications in quantum information processing, photonics, and biology. Here we report the optoelectronic investigation of shallow silicon vacancy (SiV) color centers in ultra-thin (7⁻40 nm) nanocrystalline diamond (NCD) films with variable surface chemistry. We show that hydrogenated ultra-thin NCD films exhibit no or lowered SiV photoluminescence (PL) and relatively high negative surface photovoltage (SPV) which is ascribed to non-radiative electron transitions from SiV to surface-related traps. Higher SiV PL and low positive SPV of oxidized ultra-thin NCD films indicate an efficient excitation-emission PL process without significant electron escape, yet with some hole trapping in diamond surface states. Decreasing SPV magnitude and increasing SiV PL intensity with thickness, in both cases, is attributed to resonant energy transfer between shallow and bulk SiV. We also demonstrate that thermal treatments (annealing in air or in hydrogen gas), commonly applied to modify the surface chemistry of nanodiamonds, are also applicable to ultra-thin NCD films in terms of tuning their SiV PL and surface chemistry.

• Klíčová slova
• Kelvin probe force microscopy, color center, diamond, nanocrystalline diamond, silicon-vacancy center, surface photovoltage,
• Publikační typ
• časopisecké články MeSH