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• n -p heterojunction of TiO 2 -NiO ultrafine core-shell nanoparticles are prepared. • Strong interfacial interaction significantly improve charge separation efficiency. • As-fabricated photocatalyst exhibits excellent H 2 production from water splitting. • H 2 , CH 4 and fatty acids are cogenerated from biomass lignin photoreforming. Hydrogen evolution from biomass photoreforming has been widely recognized as a promising strategy for relieving the pressure from energy crisis and environmental pollution, as it could generate sustainable H 2 and value-added bioproducts simultaneously. Combining p-type semiconductors with n -type semiconductors to form n -p heterojunction is an effective strategy to improve the photocatalytic quantum efficiency by enhancing the separation of photogenerated electrons and holes, which could greatly facilitate the realization of such biomass photorefinery concept. However, the incompact contact between the n -type and p-type semiconductors often induces the aggregation of photogenerated electrons and holes. In this work, we design and synthesize an ultrafine n -p heterojunction TiO 2 -NiO core-shell structure to overcome the incompact contact in the n -p interface. When the n -p heterojunction photocatalysts are evaluated for photocatalytic water splitting and biomass lignin photoreforming respectively, the as-fabricated TiO 2 -NiO nanocomposite with 3.25% NiO demonstrates the highest hydrogen generation of 23.5 mmol h−1 g−1 from water splitting and H 2 (0.45 mmol h−1 g−1) and CH 4 (0.03 mmol h−1 g−1) cogeneration with reasonable amount of fatty acids (palmitic acid and stearic acid) production from lignin photoreforming. The excellent photocatalytic activity is ascribed to the synergistic effects of high crystallinity of TiO 2 ultrafine nanoparticles, core-shell structure and n -p heterojunction with NiO nanoclusters. This present work demonstrates a simple and efficient method to fabricate ultrafine n -p heterojunction core-shell structure for noble-metal free catalyst for both water splitting and biomass photoreforming. [ABSTRACT FROM AUTHOR]

Graphical abstract Hierarchically porous ZnO/g-C 3 N 4 microspheres with type-II heterojunction exhibit an enhanced photocatalytic degradation on rhodamine B and phenol. Abstract Graphitic carbon nitride (g-C 3 N 4) is a visible light active semiconductor. However, low conductivity and high recombination rate of photogenerated electrons and holes limit its application in photocatalysis. In this work, we design and synthesize hierarchically porous zinc oxide/graphitic carbon nitride (ZnO/g-C 3 N 4) microspheres with type-II heterojunction to effectively degrade rhodamine B (RhB) via increasing the charge-separation efficiency. The ultraviolet-visible (UV–Vis) absorption spectra, Mott-Schottky plots and valence band X-ray photoelectron spectroscope confirm the formation of type-II heterojunction between ZnO nanocrystals and g-C 3 N 4 nanosheets. As a result, the 1.5-ZnO/g-C 3 N 4 composite (the mass ratio of zinc acetate dihydrate to g-C 3 N 4 is 1.5) exhibits the highest photocatalytic activity with good stability and higher photocatalytic degradation rate comparing to pure g-C 3 N 4 and pure ZnO. In addition, our results confirm that O 2 − and h+ are the main active species for ZnO/g-C 3 N 4 in degradation of RhB. [ABSTRACT FROM AUTHOR]