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Highlights: An atomically dispersed catalyst with unprecedented N8V4 Co-Ni dual-metal sites is synthesized, which shows interesting asymmetric in situ structural evolution and serves as a quasi-bifunctional catalyst for water splitting. The flexible C–OH groups generated by in situ oxidation can reversibly turn on/off the hydrogen-bonding interaction with the oxygen evolution reaction intermediates to break the conventional scaling relationship. The real structure and in situ evolution of catalysts under working conditions are of paramount importance, especially for bifunctional electrocatalysis. Here, we report asymmetric structural evolution and dynamic hydrogen-bonding promotion mechanism of an atomically dispersed electrocatalyst. Pyrolysis of Co/Ni-doped MAF-4/ZIF-8 yielded nitrogen-doped porous carbons functionalized by atomically dispersed Co–Ni dual-metal sites with an unprecedented N8V4 structure, which can serve as an efficient bifunctional electrocatalyst for overall water splitting. More importantly, the electrocatalyst showed remarkable activation behavior due to the in situ oxidation of the carbon substrate to form C–OH groups. Density functional theory calculations suggested that the flexible C–OH groups can form reversible hydrogen bonds with the oxygen evolution reaction intermediates, giving a bridge between elementary reactions to break the conventional scaling relationship. [ABSTRACT FROM AUTHOR]

To improve the light-harvesting capability and electron-hole separation efficiency, a novel heteroatom-introduced Bi 2 WO 6 photocatalyst (OV–Bi 2 WO 6) with oxygen vacancies (OVs) was prepared via the partial substitution of O2− by S2− anions. The OV-Bi 2 WO 6 showed high photocatalytic properties in photo-oxidation/reduction reactions under visible-light. The OVs content could be controlled by adjusting the sulfur source amount, and the optimal OV (0.9) -Bi 2 WO 6 with suitable OVs had a high photocatalytic activity with 97.6% of MO removal and 88.2% of Cr(VI) removal efficiency. Density functional theory (DFT) calculations verified that the OVs in Bi 2 WO 6 could induce a new defect level to decrease the bandgap energy and accelerate the carrier separation/migration. Furthermore, the possible photocatalytic mechanisms for MO degradation and Cr(VI) reduction over the OV-Bi 2 WO 6 were proposed, respectively. The present work helped us to better understand the enhancement mechanism of OVs in Bi-based semiconductors and paved the way to develop high-performance photocatalysts for environmental remediation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amorphous/crystalline heterophase W-Zn(Ti)O was successfully constructed. • W-Zn(Ti)O heterophase structure consisted of W,Ti amorphous and ZnO crystalline. • The electronic structure was adjusted by calcination topological transformation. • W-Zn(Ti)O exhibited suitable photo-oxidation/reduction activities. A new approach for constructing amorphous/crystalline heterophase W-Zn(Ti)O photocatalyst was develpoed via calcination topological transformation of the self-sacrificial WO 4 2−-pillared ZnTi-LDH (WO 4 -LDH) precursor together with in-situ W-doping. The amorphous/crystalline heterophase formation could expose enriched active sites, which promoted the transfer and separation of photogenerated e −- h + pairs. Density functional theory (DFT) calculations further verified that in-situ W-doping regulated the electronic structure and reduced bandgap energy, which made the transport of photogenerated carriers more rapid. Benefiting from the construction of the amorphous/crystalline heterophase, the W-Zn(Ti)O had suitable photo-oxidation/reduction activities, achieving 99.7% removal rate for Cr(VI) reduction, 78.1% for TC oxidation, and simultaneous Cr(VI) reduction (78.0% removal) and TC oxidation (63.2% removal) for 120 min under visible-light. This work provides a new idea for the design of amorphous/crystalline heterophase nanomaterials. [ABSTRACT FROM AUTHOR]

The Cu 2 O/ZnTi-LDH (Cu 2 O/LDH) composite was synthesized via Cu-doping into the ZnTi-LDH followed by in-situ reduction strategy for Cr(VI) reduction and tetracycline (TC) degradation under visible-light, where the Cu 2 O nanoparticles (NPs) were homogeneously embedded onto the LDH host layers through in-situ reducing the Cu-doped ZnTi-LDH (CuZnTi-LDH). The optical, photoelectric and photocatalytic performances of the Cu 2 O/LDH could be adjusted by changing the Cu-doping amount in the CuZnTi-LDH. As expected, the optimal Cu 2 O/LDH 0.10 exhibited high photocatalytic activities for the Cr(VI) reduction (95.5% Cr(VI) removal) and TC degradation (71.6% TC removal) after 120 min. Based on the experimental and density functional theory (DFT) calculation results, a possible p-n heterostructure formation between Cu 2 O and ZnTi-LDH as well as the transfer route of photogenerated electron-hole pairs toward for Cr(VI) reduction and TC degradation were proposed. This work may provide a rational and facile strategy for improving the LDH-based materials in catalytic oxidation-reduction reactions. The schematic diagram of the evolution process of the Cu 2 O/ZnTi-LDH, and photocatalytic of Cr(VI) reduction and TC degradation under visible-light. [Display omitted] • Cu 2 O NPs were evenly embedded onto the LDH host layers by in-situ reduction strategy. • Cu 2 O self-photooxidation was restrained due to the high dispersion of Cu 2 O NPs. • The p-n heterostructure provided a new path for transfer and separation of electron-hole pairs. • Cu 2 O/ZnTi-LDH displayed excellent Cr(VI) reduction and TC degradation performances. [ABSTRACT FROM AUTHOR]