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Detailed investigation of photocatalysts, cocatalysts and redox mediators provides a Z-scheme overall water splitting system operating under long-wavelength visible light.

In a Rh/CrOx core–shell cocatalyst for water-splitting photocatalysts, CrOx serves as an electron pathway, transfers the photoexcited electrons from photocatalysts to Rh (reduction site), and improves the H2 evolution activity.

Barium tantalum oxynitride (BaTaO2N), a photocatalyst active during one-step-excitation overall water splitting under visible light, was synthesized by NH3-based nitridation of a mixture of BaCO3 and amorphous Ta2O5·3H2O.

Non-fused electron-accepting π-conjugated compounds have been investigated recently for application to nonfullerene acceptors (NFAs) in organic solar cells (OSCs). However, the establishment of rational molecular design for non-fused NFAs is still lagging because the influence of flexible non-fused structures on the dynamics of electron–hole pairs in OSCs is not entirely understood. In this study, we utilized cyclopentene-annelated thiophene with spiro-substituted 2,7-bis(2-ethylhexyl)fluorene (FT) as a rigid and sterically bulky linker unit and developed a non-fused NFA (TT–FT–DCI) containing FT units. Photophysical measurements indicated that the introduction of the FT unit leads to the formation of rigid molecular structure. OSCs based on donor polymer (PBDB-T) and TT–FT–DCI showed an improved power conversion efficiency of 7.13% due to the increase in the short-circuit current density and fill factor. Time-resolved optical and microwave spectroscopies showed that the FT unit contributes to the long lifetimes of excited state and charge-separated state in the PBDBT:TT–FT–DCI blend films. Time-resolved electron paramagnetic resonance measurements showed that the distant charge-separated states of the face-to-face PBDB-T:TT–FT–DCI structure, which is derived by avoiding over-crystallization by the steric bulkiness of TT–FT–DCI, can interact with the cathodes for preferential electron injection following charge generations. This study highlights that by using the rigid π-conjugated framework and suppressed self-aggregation of the non-fused acceptor, effective molecular design for the appropriate dynamics of photocurrent generation is possible.

Defects in powder photocatalysts determine the photocatalytic activity. The addition of defects sometimes enhances the activity, but sometimes decreases it. However, the factors determining the difference between these cases have not been fully elucidated yet. Herein, we investigated the effects of oxygen vacancies on photocarrier dynamics in WO3 powder using broadband transient absorption spectroscopy. It was found that the decay of deeply trapped electrons was accelerated when the number of oxygen vacancies was increased by H-2 reduction. This result suggests that oxygen vacancies in WO3 mainly act as recombination centers. This is in contrast to many other photocatalysts such as TiO2 and SrTiO3, where the carrier lifetime increases with increasing oxygen vacancy concentration. These differences can be attributed to the difference in the distance between oxygen vacancies. When defects are dispersed, trapped electrons need to travel over long distances by repeatedly hopping and tunneling between defects to combine with holes, resulting in decelerated recombination. In contrast, when the defects are connected or located close together, the trapped electrons can readily migrate among defects, leading to enhanced recombination. Control of the distance between defects is thus important for enhancing photocatalytic activity.

Photoexcited charge manipulation was demonstrated by molecular engineering in conjugated polymers, bearing a Ru(ii) complex as the CO2 reduction photocatalyst.

Pulverization followed by annealing treatment improved the activity of BiVO4 although the annealing treatment had a negative impact on the non-milled sample.

An efficient spatial separation of photoexcited carriers is demonstrated in a layered-oxyhalide nanoplate by controlling the direction of carrier flows upon Rh cocatalyst loading, which leads to drastic photocatalytic H2 evolution activity.

Providing affordable safe drinking water and universal sanitation poses a grand challenge especially after the global COVID-19 pandemic. In this work, we developed atomically dispersed Au on potassium-incorporated polymeric carbon nitride (AuKPCN) that could simultaneously boost photocatalytic generation of ·OH and H2O2 with an apparent quantum efficiency over 90% at 400–420 nm. The introduction of potassium into the poly(heptazine imide) matrix formed strong K-N bonds, preventing Au from forming strong interactions with N. Instead, Au formed a bond with C, only having weak interactions with N on KPCN, which rendered Au with an oxidation number close to 0. The results of in-situ vibrational spectroscopy, isotopic experiments, transient absorption spectroscopy and time-dependent density functional theory (TDDFT) simulations revealed that the low-valent Au could append its 6s orbital into the band diagram of AuKPCN that formed a trapping level for generating highly localized holes under photoexcitation. These highly localized holes could boost the 1e− water oxidation reaction to form highly oxidative ·OH and simultaneously unbind the hydrogen atom in H2O molecule, which greatly promoted the hydrogenation process during the 2e− oxygen reduction reaction (ORR) to produce H2O2. The photogenerated ·OH on AuKPCN led to a more than 120-fold efficiency enhancement for visible-light-response superhydrophilicity as compared to that of the commercial TiO2. The onsite fixed-bed reactor under photo-illumination achieved a remarkable 132.5 LH2O m− 2 day− 1 water disinfection rate (lg6), which is about 30 times superior than the TiO2 photocatalytic advanced oxidation process in the most ideal case (H2O m− 2 day− 1; lg4).

Co-doping a La5Ti2Cu0.9Ag0.1O7S5(LTCA) photocatalyst with Ga3+ and Al3+ increases hole conductivity and facilitates electron transfer to the Rh cocatalyst.

Terminal-group halogenation is an effective strategy for tuning energy levels, improving light-harvesting ability, and enhancing the intermolecular stacking of nonfullerene acceptors (NFAs) for org...

Among 600 nm class transition-metal oxynitrides, BaTaO2N with a cubic Pm3m perovskite-type structure is promising for solar water oxidation due to its absorption of visible light up to 660 nm, nar...

Charge separation is crucial for an efficient artificial photosynthetic process, especially for narrow-bandgap metal sulfides/selenides. The present study demonstrates the application of a p-n junction to particulate metal selenides to enhance photocatalytic Z-scheme overall water splitting (OWS). The constructed p-n junction of CdS-(ZnSe)0.5(CuGa2.5Se4.25)0.5 significantly boosted charge separation. A thin TiO2 coating layer also was introduced to inhibit photocorrosion of CdS and suppress the backward reaction of water formation from hydrogen and oxygen. By employing Pt-loaded TiO2/CdS-(ZnSe)0.5(CuGa2.5Se4.25)0.5 as a hydrogen evolution photocatalyst (HEP), we assembled a Z-scheme OWS system, together with BiVO4:Mo and Au as an oxygen evolution photocatalyst and electron mediator, respectively. An apparent quantum yield of 1.5% at 420 nm was achieved, which is by far the highest among reported particulate photocatalytic Z-scheme OWS systems with metal sulfides/selenides as HEPs. The present work demonstrates that a well-tailored p-n junction structure is effective for promoting charge separation in photocatalysis and opens new pathways for the development of efficient artificial photosynthesis systems involving narrow bandgap photocatalysts.

The simultaneous control of the defect species and surface properties of semiconducting materials is a crucial aspect of improving photocatalytic performance, yet it remains challenging. Here, we synthesized Mg-Zr-codoped single-crystalline Ta3N5 (Ta3N5:Mg+Zr) nanoparticles by a brief NH3 nitridation process, exhibiting photocatalytic water reduction activity 45 times greater than that of pristine Ta3N5 under visible light. A coherent picture of the relations between the defect species (comprising reduced Ta, nitrogen vacancies and oxygen impurities), surface properties (associated with dispersion of the Pt cocatalyst), charge carrier dynamics, and photocatalytic activities was drawn. The tuning of defects and simultaneous optimization of surface properties resulting from the codoping evidently resulted in the generation of high concentrations of long-lived electrons in this material as well as the efficient migration of these electrons to evenly distributed surface Pt sites. These effects greatly enhanced the photocatalytic activity. This work highlights the importance and feasibility of improving multiple properties of a catalytic material via a one-step strategy.

Artificial photosynthesis offers a promising strategy to produce hydrogen peroxide (H2O2)—an environmentally friendly oxidant and a clean fuel. However, the low activity and selectivity of the two-electron oxygen reduction reaction (ORR) in the photocatalytic process greatly restricts the H2O2 production efficiency. Here we show a robust antimony single-atom photocatalyst (Sb-SAPC, single Sb atoms dispersed on carbon nitride) for the synthesis of H2O2 in a simple water and oxygen mixture under visible light irradiation. An apparent quantum yield of 17.6% at 420 nm together with a solar-to-chemical conversion efficiency of 0.61% for H2O2 synthesis was achieved. On the basis of time-dependent density function theory calculations, isotopic experiments and advanced spectroscopic characterizations, the photocatalytic performance is ascribed to the notably promoted two-electron ORR by forming μ-peroxide at the Sb sites and highly concentrated holes at the neighbouring N atoms. The in situ generated O2 via water oxidation is rapidly consumed by ORR, leading to boosted overall reaction kinetics. Hydrogen peroxide is an interesting target for artificial photosynthesis, although its actual production via the two-electron oxygen reduction reaction remains limited. Now, a carbon nitride-supported antimony single atom photocatalyst has been developed with a superior performance for this process.

The particulate Z-scheme water splitting system involving a perovskite-type oxynitride as an O2-evolving photocatalyst has been first demonstrated using La0.5Sr0.5Ta0.5Ti0.5O2N accompanied by Ru-lo...

Photocatalytic water splitting reaction attracts considerable attention owing to their potential application to generate H2 gas from H2O by using solar energy. However, further activity enhancement...

Ga-La5Ti2Cu0.9Ag0.1O7S5 (Ga-LTCA), an oxysulfide photocatalyst, can act as a hydrogen evolution photocatalyst in Z-scheme water splitting systems in conjunction with an oxygen evolution photocatalyst (OEP) under visible light irradiation up to 700 nm. However, the overall efficiency is strongly limited by the low activity of Ga-LTCA. The present work demonstrates a drastic improvement in the H2 evolution activity of Ga-LTCA after loading small Rh cocatalyst particles exhibiting uniform dispersion and intimate contact with the photocatalyst. Using this system, an apparent quantum yield (AQY) of 11.2±0.9% at 420 nm was obtained for H2 evolution from an aqueous Na2S-Na2SO3 solution, this being the highest value yet reported for a sacrificial H2 evolution reaction using an oxysulfide photocatalyst. Following modification with a Cr2O3 layer, efficient Z-scheme water splitting was also accomplished using the cocatalyst-loaded Ga-LTCA in combination with H+/Cs+/PtOx/WO3 as the OEP, with an improved AQY of 2.4% at 420 nm.