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In this work, the photocatalysts containing oxygen-deficient molybdenum oxide and macroscopic three-dimensional porous graphitic carbon nitride phase composite (MoO 3-x /PCN) were prepared by in situ self-assembly method. The crystal phase and structure were characterized by XRD, XPS, FT-IR, SEM, and TEM measurements. Hydrogen production results showed that introducing of MoO 3-x resulted in a higher hydrogen production rate of MoO 3-x /PCN composite catalyst than that of PCN. Among them, the highest hydrogen production rate of 2336.15 μmol g−1 h−1 was achieved for MoO 3-x -10/PCN, which was 2.23 times higher than PCN (1048.00 μmol g−1 h−1). When the reaction system temperature was 100 °C, the photothermal hydrogen production rate of MoO 3-x -10/PCN was 8902.00 μmol g−1 h−1, which was 3.81 times higher than that at room temperature. PL spectra, UV–vis spectra and photoelectrochemical measurements showed that the localized surface plasmon resonance (LSPR) effect of MoO 3-x effectively enhanced the photo response range and increased the temperature of the reaction system. ESR measurements showed that he composites should follow the Z-scheme charge transfer mechanism, the electrons in the CB of MoO 3-x further migrate to the VB of PCN, which hinders the charge complexation in MoO 3-x and PCN, improving the hydrogen production activity. This study provides a new idea for constructing a plasma-based photothermal synergistic catalytic hydrogen production strategy. • MoO 3-x /PCN using in situ electrostatic self-assembly technique for photothermal and photocatalytic hydrogen evolution. • The LSPR effect effectively enhanced the photo response range and increased the temperature of the reaction system. • The highest hydrogen production rate of MoO 3-x -10/PCN, which was 2.23 times higher than PCN. [ABSTRACT FROM AUTHOR]

[Display omitted] • Doped RP structure perovskite was successfully constructed. • A-site doping will lead to changes in defect concentration. • B-site doping modulates the CB edge position and bandgap. • The synergistic effect create new routes for e- migration. • The catalyst has good chemical stability. The doping of certain exotic metal ions in photocatalysts may produce surface defects (such as oxygen vacancies) as well as bandgap changes, which may play an important role for their photocatalytic performance. In this work, bandgap modulation by precise control of defect concentration and transition metal oxidation state mainly owning to A-site doping and the B-site cations were achieved for the Ruddlesden-Popper structure (La 2 NiO 4). The effects of K+, Sr2+, Co2+, Mn2+ single-mental doping and co-doping on the photocatalytic activity of La 2 NiO 4 photocatalysts were investigated. It was found that the co-doping samples had a significant synergistic effect on the optical properties and photocatalytic activity of La 2 NiO 4 photocatalysts. All the single-metal-doped La 2 NiO 4 photocatalysts exhibited higher photocatalytic activity than their pristine counterpart. Moreover, the Sr2+, Co2+ co-doped La 2 NiO 4 exhibited the best optical properties, photocatalytic activity and a the hydrogen production rate of La 1.9 Sr 0.1 Ni 0.8 Co 0.2 O 4+δ more than 29 times of pure La 2 NiO 4 , has been achieved. Further analysis indicates that the surface oxygen vacancies as active sites promote efficient separation and migration of photogenerated carriers. The co-doped photocatalyst not only has a narrower bandgap, but also owns a more favorable conduction band position for photoinduced electron reduction. Overall, this work provides a simple method for introducing oxygen defects and bandgap modulation in Ruddlesden-Popper structure through metal ion doping. It is also expected to enlarge the understanding of the structure-dependence of the photocatalytic performance of perovskite materials. [ABSTRACT FROM AUTHOR]

Developing appropriate photocatalyst with high efficiency is still the basic strategy for practical application of emerging technology. Herein, non-noble metal copper (Cu) nanoparticles were in situ hybrided with TiO 2 by a chemical reduction method. The crystal phase and structure were characterized by XRD, SEM, and TEM measurements. Hydrogen production results showed that Cu nanoparticles significantly improved the photocatalytic hydrogen production rate. The hydrogen production rate was as high as 24160.69 μmol g−1 h−1 at 100 °C, which was 36.25 and 8.46 times higher than the hydrogen production rates of pure TiO 2 and 0.13 wt% Cu/TiO 2 at room temperature, respectively. PL spectra, UV–vis spectra, IR images and photoelectrochemical measurements showed that the plasma-induced photothermal effect of Cu/TiO 2 nanoparticles, which raised the temperature of the reaction system and promoted photothermal catalytic performance. Briefly, this work provides a facile fabrication method of noble-metal-free photocatalysts featuring in low-cost and high efficiency. In the future, coupling the photothermal effect of plasmonic Cu to further speed up the kinetics should be another promising research direction for further improving hydrogen production. • Non-noble metal copper (Cu) nanoparticles were in situ hybrided with TiO 2. • The crystal phase and structure were characterized by XRD, SEM, and TEM. • Results showed Cu nanoparticles improved the photocatalytic hydrogen production. • Plasma-induced photothermal effect of Cu/TiO 2 nanoparticles raised temperature. • A facile fabrication method of noble-metal-free photocatalysts is performed. [ABSTRACT FROM AUTHOR]

• Overpotential shifts from activation dominance to ohmic dominance. • Peak voltage U 0 , valley U 1 and Δ U increase proportionally with bubble detachment radius. • Study of applied current and electrolyte concentration effects on bubble evolution. • A balance of forces was established to clarify hydrogen bubble detachment behavior. • Ohmic overpotential scales with bubble size and activation scales with contact size. To understand the relationship between electrolytic hydrogen bubble evolution and electric potential fluctuations, a synchronized measurement system, comprising a high-speed camera and an electrochemical workstation, was employed to analyze single hydrogen bubble evolution on a microelectrode and investigate the voltage–time characteristics of a typical hydrogen evolution reaction. The results show periodic potential fluctuations caused by the periodic evolution of single hydrogen bubbles. The overpotential fluctuation during single bubble evolution exhibits two stages: an initial increase (Stage I) followed by a decrease (Stage II). The duration of Stage I decreases with increasing applied current. Subsequently, a balance of known forces was developed to clarify the critical roles of the Marangoni effect and electric force in bubble detachment dynamics, enabling the prediction of bubble detachment size. Furthermore, it was observed that, during single bubble evolution, the overpotential shifts from activation dominance to ohmic dominance. The magnitude of ohmic overpotential correlates with the bubble diameter, whereas activation overpotential correlates with the bubble's contact diameter. This study contributes to the understanding of activation and ohmic overpotentials linked to bubble evolution in water electrolysis devices, thereby facilitating the development of more efficient multiphase electrochemical reactors. [ABSTRACT FROM AUTHOR]

Endowing photocatalyst with functional nanostructure can effectively improve its performance towards solar energy conversion. Here, a unique Ni–Fe-based mesoporous hollow spherical nanostructure (NiFeOx/NC-t) was facilely constructed via the direct thermal decomposition of Ni-BTC@PBA composites. The hybrids consist of in-situ formed nitrogen-enriched carbon layers constituting the mesoporous walls of hollow spherical, and amorphous NiFeO x nanoparticles and a small fraction of FeNi 3 are embedded on the spherical walls during carbonization. After loading EY molecules on NiFeOx/NC-t as solar light absorbers, an optimal photocatalytic hydrogen evolution rate of 5352.7 μmol g−1 h−1 was achieved with excellent stability under visible light (λ > 420 nm) in the absence of co-catalyst. The excellent photocatalytic activity was revealed to be ascribed to: ⅰ) mesoporous hollow spherical structure having a large surface area, thus exposing more active sites; ⅱ) efficient injection of photo-generated electrons from excited EY− into NiFeO x and FeNi 3 by the bridge of high-conductive nitrogen-enriched carbon layer. In brief, the structural and compositional features synergistically strengthen the photocatalytic activity of NiFeOx/NC-t. It is worth noting that MOF-derived route can significantly simplify the preparation process of mesoporous hollow spherical nanostructure. This work provides an approach for facile preparation of versatile photocatalysts with high efficiency for solar energy conversion. • A Ni–Fe-based mesoporous hollow spherical nanostructure was facilely constructed. • The catalyst shows efficient photocatalytic H 2 evolution rate under visible light. • Excellent stability of catalyst was investigated for photocatalytic H 2 production. • The unique nanostructure has great impact on the performance of catalyst. [ABSTRACT FROM AUTHOR]

The schematic diagram for the photocatalytic H 2 evolution of x-wt% Ni/t-TiO 2. [Display omitted] • Ni/t-TiO 2 heterostructure catalyst with oxygen vacancies were facilely constructed. • High conductivity of metallic Ni improves the mobility of charge carriers. • Oxygen vacancies in the catalyst enhance the separation of photogenerated carriers. • Mesoporous structure is beneficial to improve adsorption and surface reaction. Designing photocatalysts with interfacial design and defect engineering are crucial to improved H 2 -evolution efficiency of photocatalytic water splitting. Herein, mesoporous tablet-like x-wt% Ni/t-TiO 2 catalysts with Schottky junction and oxygen vacancies (Oν) were constructed using metal–organic framework (namely MIL-125(Ti)) as template. It is demonstrated that the optimal composition of 1 wt% Ni/t-TiO 2 achieves a H 2 production rate of 4276.13 μmol/g/h without using noble metal Pt. It was ∼129 times higher than MIL-125(Ti) derived pure TiO 2 (t-TiO 2) and showed fair durability after least four consecutive cycles test under full spectrum light irradiation. Particularly, its apparent quantum efficiency (AQE) at 350 nm reaches 12.09 %. Our results show that the synergetic effect of Schottky junction and oxygen vacancies (Oν) contribute significantly to the high catalytic performance. Meanwhile, the mesoporous structure provides a large specific surface area which is crucial for further enhancement of the reaction rate. This work opens an effective and low-cost strategy for preparing novel heterojunction photocatalysts with abundant oxygen vacancies and improving the hydrogen generation rate of MOF-derived photocatalysts without using noble metal. [ABSTRACT FROM AUTHOR]

• Three-dimensional lettuce-like g-C 3 N 4 with maleic hydrazide-based molecule doping was designed. • Diazine organic groups of maleic hydrazide occupied the positions of partial tris-triazine units. • An effective charge transfer channel was formed in the in-plane structure. • The lettuce-like structure provided the ultrahigh surface area (287.37 m2 g−1) and reduced the migration distance of carriers. • The obtained superior photocatalytic activity (7689.6 μmol h−1 g−1) was 31.5 times that of pristine g-C 3 N 4. A three-dimensional (3D) lettuce-like g-C 3 N 4 with maleic hydrazide-based molecule doping was successfully developed. Based on systematic physicochemical characterizations and density functional theory (DFT) calculation, it was found that the diazine organic groups of maleic hydrazide, which occupied the positions of partial tris-triazine units, participated in the construction of valence band maximum (VBM) and promoted the formation of effective charge transfer channel from the diazine organic group in maleic hydrazide to the adjacent tris-triazine unit to promote the generation and separation of photo-generated carriers. Meanwhile, the 3D lettuce-like microstructure constituted by thin g-C 3 N 4 nanosheets could shorten the migration distance of carriers to further inhibit the recombination of photo-generated carriers, and also bring the ultrahigh surface area to provide more active sites for photocatalytic reaction. The superior visible-light-driven photocatalytic H 2 -evolution activity was obtained (7689.6 μmol h−1 g−1), which was 31.5 times that of unmodified g-C 3 N 4 , and the apparent quantum efficiency was up to 8.53 % at 425 nm. [ABSTRACT FROM AUTHOR]