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The electron density on the catalyst surface has a great influence on the multi-electron transport process of photocatalytic reduction of CO 2. In this work, hierarchical Cu 2 O/Ni-MOF composite photocatalyst with local surface plasmon resonance (SPR) properties was prepared by simple hydrothermal and water bath methods. Through DRS, XPS and AES tests found that the SPR of Cu0 expanded the light absorption, provided hot electrons for the reaction system, and greatly improved the photocatalytic activity in coordination with the hierarchical structure and heterostructure. In the absence of sacrificial agent, the CO yield of 30%-Cu 2 O/Ni-MOF was 4.1 times of Cu 2 O (5.32 μmol/g) and 11.1 times of Ni-MOF (1.95 μmol/g), respectively. Then, the possible photocatalytic reaction path was simply speculated based on in-situ FT-IR. In conclusion, the hierarchical structure, heterostructure and SPR effect accelerate the kinetics of Cu 2 O/Ni-MOF photocatalytic reaction, thus improving its photocatalytic activity. [Display omitted] • The 3D hierarchical heterogeneous Cu 2 O/Ni-MOF with SPR effect was synthesized by a simple strategy. • Cu 2 O was uniformly dispersed due to heterogeneous nucleation sites provided by 3D Ni-MOF. • SPR effect of Cu0 provides additional electrons for the reaction system to participate in the CO 2 reaction. [ABSTRACT FROM AUTHOR]

In this work, efficient NiO nanoparticles/TiO 2 nanorods p-n heterojunction structure photocatalyst is constructed by reasonable design of two-step calcination technology and examined for hydrogen production activity from methanol-water mixture. In the NiO/TiO 2 heterojunction structure small NiO nanoparticles are evenly distributed on the surface of TiO 2 and tightly connected together with TiO 2 , as it was determined by microscope characterization techniques, which conducive to the interface transport of photogenerated carriers. The novelty of this paper is the detailed characterization of NiO/TiO 2 photocatalysts by electrochemical technics as Transient photocurrent response, Mott-Schottky plots, linear sweep voltammograms and Electrochemical impedance spectroscopy and their correlation with photoactivity. The rationally designed NiO/TiO 2 p-n heterojunction promotes the transfer of photogenerated electrons and inhibits carrier recombination. The highest hydrogen production was exhibited in the presence of the 2-NiO/TiO 2 composite during 3 h of UV irradiation (701 μmol/g cat.), which exceeded the activity of pure TiO 2 by more than 1.3 times. The loss of photocatalytic hydrogen yield is negligible after repeating cycle reactions. Finally, a possible p-n heterojunction photocatalytic reduction mechanism has been discussed and apparent quantum yield was calculated. [Display omitted] • NiO nanoparticles/TiO 2 nanorods p-n heterojunction photocatalyst was constructed. • NiO/TiO 2 exhibited higher photoactivity for H 2 production in comparison with TiO 2. • Correlation of photoelectrochemical measurements with photoactivity of NiO/TiO 2. • NiO/TiO 2 p-n heterojunction inhibits carrier recombination. • Apparent Quantum Yields were calculated. [ABSTRACT FROM AUTHOR]

Wide-light absorption performance and efficient carrier separation ability are the necessary conditions for excellent photocatalytic materials. In this research, g-C 3 N 4 QDs (CN QDs) and Au nano-particles (NPs) co-modified CeO 2 /Fe 3 O 4 micro-flowers (MFs) photocatalyst (CACeF) has been prepared. CO 2 photoreduction experiments showed that the composite had obviously enhanced photoreduction activity and photocatalytic stability. The yields of CO and CH 4 over it as catalyst in 4 h is about 5 and 8 times greater than that of pure CeO 2. Photoelectrochemical tests showed that the heterojunction between CN QDs and Au NPs can greatly improve the carrier separation ability and the light-utilization efficiency of photocatalysts. Besides, the excellent electronic transmission performance of Au NPs provided a specific channel for the electron transmission, and the strong local surface plasmon resonance (LSPR) of Au NPs resulted in a lot of hot-electrons can directly take part in the CO 2 photoreduction. The synergistic effect between CN QDs and Au NPs can further enhance the photocatalytic activity of the photocatalyst. Fe 3 O 4 QDs can ensure the effective recovery and reuse of the composite without affecting the photocatalytic performance of composite. Finally, a potential photoreduction mechanism of CN QDs and Au NPs co-modified CeO 2 /Fe 3 O 4 MFs photocatalyst were discussed in total. [Display omitted] • g-C3N4 QDs/Au NPs/CeO2/Fe3O4 has been prepared for the CO2 photoreduction. • Light-absorption performance of photocatalyst has been greatly enhanced. • Au efficiently speeds up the electrons' generation efficiency in semiconductors. • Synergistic effect of CN QDs/Au NPs enhanced the photoreduction performance. • Fe3O4 QDs can ensure the recovery without affecting the photocatalytic performance. [ABSTRACT FROM AUTHOR]

The interfacial regulation strategy between semiconductors can effectively promote the separation efficiency of photogenerated carriers and enhance photocatalytic activity under the synergistic effect. Herein, AgInS 2 QDs-MoS 2 /GO (AIS-MS/GO) composites were prepared by interfacial coupling of AgInS 2 QDs (AIS), hierarchical MoS 2 and ultrathin GO. Ultrathin GO successfully solved the agglomeration problem of AIS and hierarchical MoS 2. Moreover, the photogenerated carriers were effectively separated and transferred under the synergistic effect of the AIS-MS heterojunction and ultrathin GO, thus promoting tetracycline (TC) degradation and CO 2 reduction performance. The degradation rate of tetracycline (TC) reached 96.5 %, and the yields of CO and CH 4 in the CO 2 reduction products reached 52.6 and 28.5 μmol g–1, respectively, when using the optimized photocatalyst. In-situ FTIR analysis indicated that TC is gradually degraded by small molecules on the composite surface, and has excellent dissociation ability of water molecules during the CO 2 reduction process. This work provides a new vision for the rational design of heterojunction-based photocatalysts using the interfacial regulation strategy for enhancing interfacial charge separation and photocatalytic performance. [Display omitted] • AIS-MS/GO composites were prepared via the interfacial regulation strategy. • The photogenerated carriers were effectively separated and transferred under synergistic and interfacial effects. • The aggregation problem of AIS and hierarchical MoS 2 was effectively solved. • AIS-MS/GO composites achieve a 96.5 % TC degradation rate and 35.1 % selectivity for CH 4. [ABSTRACT FROM AUTHOR]

The 3D hierarchical structure of CdS/Ni-MOF inhibits the agglomeration of CdS, improve light harvesting, increase active surface area, reaction sites, promote charge transfer and separation, which greatly improves the efficiency of CO 2 conversion. However, when the CdS is overloaded and its hierarchical structure is destroyed, the heterostructure plays a major role in improving the performance. Based on the above results, we propose the preliminary mechanism of 20%-CdS/Ni-MOF photocatalytic reduction of CO 2. Firstly, under UV–Vis illumination, Ni-MOF and CdS are excited to produce electrons (e−) and holes (h+). Then, because of the tight interface contact, the e- excited by Ni-MOF could be transferred to CdS with more positive CB, and CdS as the active site could reduce CO 2 to CO more effectively. At the same time, the h+ in the VB of Ni-MOF and CdS participate in the oxidation reaction to produce O 2 and H 2 O 2 , which achieving the elimination of holes. Such charge separation and transfer of the electron-hole pairs facilitate enhanced photocatalytic activity. [Display omitted] • The 3D hierarchical heterostructure was synthesized by a simple strategy. • 20%-CdS/Ni-MOF showed excellent performance in the vapor–solid reaction system. • The hierarchical structure and heterostructure of CdS/Ni-MOF play a synergistic role. Fabricating the hierarchical heterostructure is efficient way for enhancing CO 2 conversion of semiconductor photocatalysts. Herein, a simple strategy has been employed to prepare several 3D hierarchical CdS/Ni-MOF heterostructure photocatalysts, and the selective photoreduction of CO 2 to CO under simulated sunlight in the gas–solid phase reactor. Among the prepared photocatalysts, 20%-CdS/Ni-MOF shows the best CO yield, which was 16 times and 7 times that of Ni-MOF and CdS, respectively. By controlling the morphology of the catalyst, we found that the significant improvement in photocatalytic activity can be ascribed to the synergistic effect of heterostructure in CdS/Ni-MOF and its unique hierarchical structure, which can improve the efficiency of charge transmission and provides abundant active sites, etc. Finally, the preliminary photocatalytic mechanism was discussed by in situ FTIR and liquid ultraviolet spectrophotometer. [ABSTRACT FROM AUTHOR]