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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]

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]

• 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]

• 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]