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The rational design of durable and nonprecious nanocomposite photocatalysts with efficient charge separation and abundant active sites is still a grand challenge for photocatalytic hydrogen production from water reduction. Herein, a novel ternary nanocomposite, MoO 2 decorated Mn 0.5 Cd 0.5 S/Cu 2 O p-n heterojunction has been constructed via a facile two-step route employing the energy band engineering theory. Impressively, the optimized ternary Mn 0.5 Cd 0.5 S/Cu 2 O/MoO 2 nanocomposite displays a robust photocatalytic H 2 -evolution rate of 733.24 μmol h−1 under simulated solar light irradiation, more 4.2 times higher than pure Mn 0.5 Cd 0.5 S. The results demonstrated that the p-n heterojunction formed between n-type Mn 0.5 Cd 0.5 S and p-type Cu 2 O could markedly promote the interfacial charge transfer/separation through the internal electric field, whereas the MoO 2 cocatalyst with low overpotential could effectively collect photoinduced electrons and dramatically facilitate the H 2 -evolution kinetics. Moreover, both Cu 2 O and MoO 2 could improve the light-harvesting ability of pristine Mn 0.5 Cd 0.5 S, further contributing to the boosted hydrogen generation activity. [Display omitted] • MoO 2 decorated Mn 0.5 Cd 0.5 S/Cu 2 O p-n heterojunction synthesized for H 2 -production. • Multichannel charge-carrier transfer between Mn 0.5 Cd 0.5 S, Cu 2 O and MoO 2 discussed. • High H 2 -production rate achieved over composite, 4.2 folds higher than Mn 0.5 Cd 0.5 S. [ABSTRACT FROM AUTHOR]

• Au decorated S-scheme Mn 0.5 Cd 0.5 S/WO 3 composite synthesized for H 2 -production. • Mechanism of charge transfer and separation in Au decorated S-scheme discussed. • High H 2 -production rate achieved over composite, 2.74 folds higher than Mn 0.5 Cd 0.5 S. Spontaneously solar-driven H 2 -production from water reduction provides a promising strategy to solve the aggravating energy and environment crises worldwide, but it is severely limited by the rapid charge-carrier recombination and the slashing redox potentials requirement. Here, a new ternary Mn 0.5 Cd 0.5 S/WO 3 /Au heterostructure photocatalyst has been designed by chemical deposition of Au nanoparticles (NPs) on Mn 0.5 Cd 0.5 S/WO 3 step-scheme (S-scheme) composite matrix to boost the photocatalytic activity through the multichannel-enhanced charge transfer/separation. By optimizing the constituent of the heterostructure photocatalyst, the prepared Mn 0.5 Cd 0.5 S/WO 3 /Au photocatalyst with 30 wt% of WO 3 and 4 wt% of Au exhibits the highest H 2 -evolution rate of 517.13 µmol h−1 under simulated solar light irradiation, more 2.74, 1.63 and 1.45 times higher than bare Mn 0.5 Cd 0.5 S and Mn 0.5 Cd 0.5 S loaded with WO 3 and Au alone, respectively. Mechanistic characterizations and control experiments have revealed that the S-scheme charge transfer in Mn 0.5 Cd 0.5 S/WO 3 heterojunction together with the "electron reservoir" resulting from the Au NPs contribute to the superior H 2 -generation activity over Mn 0.5 Cd 0.5 S/WO 3 /Au catalyst, which not only dramatically promotes the charge-carrier separation but also remains the strong redox ability of photoinduced electrons and holes in such photocatalytic system. [ABSTRACT FROM AUTHOR]

Constructing heterojunction photocatalytic systems with highly spatial charge separation, strong photoredox ability and rapid surface reaction still remains an enormous challenge. Herein, hollow CoS x polyhedrons decorated hierarchically direct Z-scheme Mn 0.5 Cd 0.5 S/CdWO 4 heterojunction photocatalyst is designed and constructed by a simple sonochemical approach and subsequent in situ deposition route. Such a constructed Mn 0.5 Cd 0.5 S/CdWO 4 /CoS x ternary composite exhibits a significantly boosted photoactivity toward H 2 generation compared to bare Mn 0.5 Cd 0.5 S, binary Mn 0.5 Cd 0.5 S/CdWO 4 , Mn 0.5 Cd 0.5 S/CoS x and Mn 0.5 Cd 0.5 S/Pt samples with optimized composition ratio. Apart from the efficient charge transfer channels and preserved strong photoredox ability within the direct Z-scheme Mn 0.5 Cd 0.5 S/CdWO 4 heterojunction, the hollow structure of CoS x polyhedrons could endow abundant surface-active sites, strengthen the light-harvesting capacity through the internal multilight scattering/reflection and decrease the overpotential for H 2 evolution, which further contributes to the boosted photoactivity toward hydrogen production. This study demonstrates an alternate methodology for constructing high-performance multi-hierarchical Z-scheme/cocatalyst heterojunction photocatalysts for solar energy conversion. [ABSTRACT FROM AUTHOR]

• A new ternary Mn 0.5 Cd 0.5 S/RGO-MoS 2 composite was successfully synthesized. • The synergetic effect between RGO and MoS 2 cocatalyst were discussed. • Mechanism of the enhanced photocatalytic activity was illuminated. A new solar-light-active ternary heterojunction photocatalyst, consisting of Mn 0.5 Cd 0.5 S nanoparticles grown on 2D reduced graphene oxide (RGO)-MoS 2 hybrid composite as a nonprecious and highly efficient cocatalyst has been successfully fabricated via a facile in-situ growth process. The optimized Mn 0.5 Cd 0.5 S/RGO-MoS 2 nanocomposite with 2 wt% RGO-MoS 2 cocatalyst displays the highest H 2 -evolution rate of 642.15 µmol h−1, which is about 3.75 times higher than bare Mn 0.5 Cd 0.5 S and far exceeding other composite photocatalysts, i.e., Mn 0.5 Cd 0.5 S/RGO, Mn 0.5 Cd 0.5 S/MoS 2 and noble Pt-modified Mn 0.5 Cd 0.5 S. It was revealed that the dramatically improved photoactivity of the ternary Mn 0.5 Cd 0.5 S/RGO-MoS 2 heterojunction photocatalyst was mainly originated from the positive cooperation between RGO and MoS 2 nanosheets. The RGO nanosheets with high conductivity could serve as an electron transport bridge to collect and transfer the photogenerated electrons effectively, while MoS 2 nanosheets with high electrocatalytic activity could act as an effective H 2 -evolution cocatalyst to facilitate the photoinduced electrons taking part in the hydrogen production reaction from water reduction, thus boosting the H 2 -evolution kinetics. More importantly, the RGO nanosheets could also lead to the downshift of the valence band (VB) of Mn 0.5 Cd 0.5 S, which was beneficial for the rapid oxidation of sacrificial agents and the interfacial charge transfer/separation, thereby helping to improve the photocatalytic performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Direct Z-scheme Mn 0.5 Cd 0.5 S/CoTiO 3 heterojunction was designed. • Mechanism for the enhanced photoactivity over Mn 0.5 Cd 0.5 S/CoTiO 3 heterojunction discussed. • High ammonia production rate achieved over heterojunction, 5.1-fold higher than Mn 0.5 Cd 0.5 S. The exploration and design of highly efficient and robust photocatalysts composed of earth-abundant materials for ambient photocatalytic N 2 fixation to ammonia remains a significant challenge. Here, we have fabricated a stable and highly efficient direct Z-scheme Mn 0.5 Cd 0.5 S/CoTiO 3 heterostructure for N 2 fixation by depositing Mn 0.5 Cd 0.5 S nanoparticles on CoTiO 3 surface. Under ambient conditions, the optimized Mn 0.5 Cd 0.5 S/CoTiO 3 heterojunction achieved a significant NH 3 production rate of 121.9 μmol g-1h−1 without cocatalyst modification, representing a 5.1- and 5.9-fold increase over pristine Mn 0.5 Cd 0.5 S and CoTiO 3 , respectively, and also exceeding most previously reported photocatalytic systems. The significant improvement in ammonia production primarily results from the Z-scheme charge transfer path between the Mn 0.5 Cd 0.5 S and CoTiO 3 components, which enables effective separation of photoinduced carriers while maintaining their robust redox capacity, thus dramatically boosting ammonia generation performance. This research may provide new insights for advancing other alternative Z-scheme photocatalytic systems with remarkable stability and exceptional efficiency in N 2 fixation. [ABSTRACT FROM AUTHOR]

The rational design of hierarchical heterojunction photocatalysts with efficient spatial charge separation remains an intense challenge in hydrogen generation from photocatalytic water splitting. Herein, a noble-metal-free MoS 2 /g-C 3 N 4 /ZnIn 2 S 4 ternary heterostructure with a hierarchical flower-like architecture was developed by in situ growth of 3D flower-like ZnIn 2 S 4 nanospheres on 2D MoS 2 and 2D g-C 3 N 4 nanosheets. Benefiting from the favorable 2D-2D-3D hierarchical heterojunction structure, the resultant MoS 2 /g-C 3 N 4 /ZnIn 2 S 4 nanocomposite loaded with 3 wt% g-C 3 N 4 and 1.5 wt% MoS 2 displayed the optimal hydrogen evolution activity (6291 μmol g−1 h−1), which was a 6.96-fold and 2.54-fold enhancement compared to bare ZnIn 2 S 4 and binary g-C 3 N 4 /ZnIn 2 S 4 , respectively. Structural characterizations reveal that the significantly boosted photoactivity is closely associated with the multichannel charge transfer among ZnIn 2 S 4 , MoS 2 , and g-C 3 N 4 components with suitable band-edge alignments in the composites, where the photogenerated electrons migrate from g-C 3 N 4 to ZnIn 2 S 4 and MoS 2 through the intimate heterojunction interfaces, thus enabling efficient electron-hole separation and high photoactivity for hydrogen evolution. In addition, the introduction of MoS 2 nanosheets highly benefits the improved light-harvesting capacity and the reduced H 2 -evolution overpotential, further promoting the photocatalytic H 2 -evolution performance. Moreover, the MoS 2 /g-C 3 N 4 /ZnIn 2 S 4 ternary heterostructure possesses prominent stability during the photoreaction process owing to the migration of photoinduced holes from ZnIn 2 S 4 to g-C 3 N 4 , which is deemed to be central to practical applications in solar hydrogen production. [ABSTRACT FROM AUTHOR]

Exploring efficient and robust photocatalysts for solar hydrogen generation from water reduction is great significant in solving the energy shortage and environment contamination simultaneously. Herein, benefiting from the matchable energy band structures and band bending, the direct Z-scheme ZnIn 2 S 4 /NiWO 4 heterojunctions were successfully constructed by anchoring p-type NiWO 4 nanoparticles onto n-type ZnIn 2 S 4 nanosheets through a facile sonochemical route. By carefully regulating the interfacial structure, the optimized ZnIn 2 S 4 /NiWO 4 heterostructure without any cocatalyst displays excellent stability and remarkably improved photocatalytic hydrogen evolution activity (16.3 mmol∙g−1∙h−1), more 3.57-folds increment than bare ZnIn 2 S 4 photocatalyst. Mechanistic characterizations demonstrate that the dramatically boosted photocatalytic performance mainly results from the constructed Z-scheme heterostructure and intimately interfacial contact between ZnIn 2 S 4 and NiWO 4 , which results in the valid interfacial charge transfer channels, powerful redox potential and reduced hydrogen evolution energy barrier, as confirmed by the joint analysis of electron spin resonance (ESR) and photoelectrochemical measurements. More importantly, the photoinduced holes of ZnIn 2 S 4 are rapidly and effectively consumed in the unique Z-scheme charge transfer channels, which greatly favors the suppression of the photocorrosion caused by insufficient hole extraction during the photocatalytic reaction, thereby promoting the overall stability and reusability of the ZnIn 2 S 4 /NiWO 4 composite photocatalyst. This study paves the way for constructing other Z-scheme nano-heterostructure consisting of p-type and n-type semiconductors with efficient photoactivity and robust stability for energy and environmental applications. [Display omitted] • Z-scheme heterojunction consisting of p-type and n-type semiconductors was designed. • Mechanism for the enhanced photoactivity over ZnIn 2 S 4 /NiWO 4 heterojunction discussed. • High H 2 -production rate achieved over heterojunction, 3.57-fold higher than ZnIn 2 S 4. [ABSTRACT FROM AUTHOR]