An enormous research effort is currently being directed towards the development of efficient visible-light-driven photocatalysts for renewable energy applications including water splitting, CO₂ reduction and alcohol photoreforming. Layered double hydroxide (LDH)-based photocatalysts have emerged as one of the most promising candidates to replace TiO₂-based photocatalysts for these reactions_, owing to their unique layered structure, compositional flexibility, controllable particle size, low manufacturing cost and ease of synthesis. By introducing defects into LDH materials through the control of their size to the nanoscale, the atomic structure, surface defect concentration, and electronic and optical characteristics of LDH materials can be strategically engineered for particular applications. Furthermore, through the use of advanced characterization techniques such as X-ray absorption fine structure, positron annihilation spectrometry, X-ray photoelectron spectroscopy, electron spin resonance, density-functional theory calculations, and photocatalytic tests, structure-activity relationships can be established and used in the rational design of high-performance LDH-based photocatalysts for efficient solar energy capture. LDHs thus represent a versatile platform for semiconductor photocatalyst development with application potential across the energy sector.

Monovalent Zn⁺ (3d¹⁰4s¹) systems possess a special electronic structure that can be exploited in heterogeneous catalysis and photocatalysis, though it remains challenge to synthesize Zn⁺-containing materials. By careful design, Zn⁺-related species can be synthesized in zeolite and layered double hydroxide systems, which in turn exhibit excellent catalytic potential in methane, CO and CO₂ activation. Furthermore, by utilizing advanced characterization tools, including electron spin resonance, X-ray absorption fine structure and density functional theory calculations, the formation mechanism of the Zn⁺ species and their structure-performance relationships can be understood. Such advanced characterization tools guide the rational design of high-performance Zn⁺-containing catalysts for efficient energy conversion.

A novel K₂Nb₂O₆ photocatalyst with pyrochlore structure has been synthesized via a facile one-pot hydrothermal route with no aid of additives. The as-prepared samples were characterized by powder X-ray diffraction, ultraviolet-visible spectroscopy and field emission scanning electron microscopy. The photocatalytic H₂ evolution was performed in an aqueous methanol solution under UV light irradiation. The as-prepared K₂Nb₂O₆ photocatalyst with pyrochlore structure showed higher H₂ production activity than that of perovskite KNbO₃ and commercial Nb₂O₅ powders in the absence of cocatalysts, due mainly to its unique crystal and energy band structures. The rate of H₂ evolution can be significantly enhanced by loading of Pt nanoparticles. The highest H₂ evolution rate of 121 µmol/h was reached when 0.7 wt% Pt nanoparticles were used, which was about 20 times higher than that of pristine K₂Nb₂O₆.

A heteroleptic bis(tributylphosphine) platinum(II)-alkynyl complex (Pt-1) showing broadband visible-light absorption was prepared. Two different visible-light-absorbing ligands, that is, ethynylated boron-dipyrromethene (BODIPY) and a functionalized naphthalene diimide (NDI) were used in the molecule. Two reference complexes, Pt-2 and Pt-3, which contain only the NDI or BODIPY ligand, respectively, were also prepared. The coordinated BODIPY ligand shows absorption at 503 nm and fluorescence at 516 nm, whereas the coordinated NDI ligand absorbs at 594 nm; the spectral overlap between the two ligands ensures intramolecular resonance energy transfer in Pt-1, with BODIPY as the singlet energy donor and NDI as the energy acceptor. The complex shows strong absorption in the region 450 nm–640 nm, with molar absorption coefficient up to 88 000 M⁻¹ cm⁻¹. Long-lived triplet excited states lifetimes were observed for Pt-1–Pt-3 (36.9 μs, 28.3 μs, and 818.6 μs, respectively). Singlet and triplet energy transfer processes were studied by the fluorescence/phosphorescence excitation spectra, steady-state and time-resolved UV/Vis absorption and luminescence spectra, as well as nanosecond time-resolved transient difference absorption spectra. A triplet-state equilibrium was observed for Pt-1. The complexes were used as triplet photosensitizers for triplet–triplet annihilation upconversion, with upconversion quantum yields up to 18.4 % being observed for Pt-1.