Photothermal CO₂ reduction is an efficient and sustainable catalytic path for CO₂ treatment. Here, we successfully fabricated a novel series of Ni-based catalysts (Ni-x) via H₂ reduction of NiAl-layered double hydroxide nanosheets at temperatures (x) ranging from 300 to 600 ℃. With the increase of the reduction temperature, the methane generation rate of the Ni-x catalyst for photothermal CO₂ hydrogenation gradually increased under ultraviolet-visible-infrared (UV–vis–IR) irradiation in a flow-type system. The Ni-600 catalyst showed a CO₂ conversion of 78.4%, offering a CH₄ production rate of 278.8 mmol·g^–1·h^–1, with near 100% selectivity and 100 h long-term stability. Detailed characterization analyses showed metallic Ni nanoparticles supported on amorphous alumina are the catalytically active phase for CO₂ methanation. This study provides a possibility for large-scale conversion and utilization of CO₂ from a sustainable perspective.

Developing low-energy input route for conversion of methane (CH₄) to value-added methanol (CH₃OH) at room temperature is important in environment and industry. Bonding in electron donor-acceptor hybrid can potentially promote charge transfer and photocatalytic efficiency of CH₄ conversion. Herein, bonding in electron donor rhodamine B (RhB)–acceptor (TiO₂) hybrid (RhB/TiO₂) significantly promotes the selectivity of photocatalytic oxidation of CH₄ to CH₃OH and utilization of visible light (low-energy photons) at ambient condition. Even under green light irradiation (λ = 550 nm), the noble-metal-free RhB/TiO₂ hybrid synthesized presents enhanced oxidation of CH₄ to CH₃OH with a generation rate of 143 ·mol·g^-1·h^-1 and selectivity of 94%. This work demonstrates the possibility and feasibility of noble-metal-free catalysts for activating CH₄ under visible light at room temperature.

Electrochemical CO₂ reduction reaction (CO₂RR) offers a practical solution to current global greenhouse effect by converting excessive CO₂ into value-added chemicals or fuels. Noble metal-based nanomaterials have been considered as efficient catalysts for the CO₂RR owing to their high catalytic activity, long-term stability and superior selectivity to targeted products. On the other hand, they are usually loaded on different support materials in order to minimize their usage and maximize the utilization because of high price and limited reserve. The strong metal-support interaction (MSI) between the metal and substrate plays an important role in affecting the CO₂RR performance. In this review, we mainly focus on different types of support materials (e.g., oxides, carbons, ligands, alloys and metal carbides) interacting with noble metal as electrocatalysts for CO₂RR. Moreover, the positive effects about MSI for boosting the CO₂RR performance via regulating the adsorption strength, electronic structure, coordination environment and binding energy are presented. Lastly, emerging challenges and future opportunities on noble metal electrocatalysts with strong MSI are discussed.

A simple one-step thermal polymerization method was developed for synthesis of holey graphitic carbon nitride nanotubes, involving direct heating of mixtures of melamine and urea or melamine and cyanuric acid in specific mass ratios. Supramolecular structures formed between the precursor molecules guided nanotube formation. The porous and nanotubular structure of the nanotubes facilitated efficient charge carrier migration and separation, thereby enhancing photocatalytic H₂ production in 20 vol.% lactic acid under visible light irradiation. Nanotubes synthesized using melamine and urea in a 1:10 mass ratio (denoted herein as CN-MU nanotubes) exhibited a photocatalytic hydrogen production rate of 1, 073.6 μmol·h^-1·g^-1 with Pt as the cocatalyst, a rate of 4.7 and 3.1 times higher than traditional Pt/g-C₃N₄ photocatalysts prepared from graphitic carbon nitride (g-C₃N₄) obtained by direct thermal polymerization of melamine or urea, respectively. On the basis of their outstanding performance for photocatalytic H₂ production, it is envisaged that the holey g-C₃N₄ nanotubes will find widespread uptake in other areas, including photocatalytic CO₂ reduction, dye-sensitized solar cells and photoelectrochemical sensors.

A template-free hydrothermal-assisted thermal polymerization method has been developed for the large-scale synthesis of one-dimensional (1D) graphitic carbonnitride (g-C₃N₄) microtubes. The g-C₃N₄ microtubes were obtained by simple thermal polymerization of melamine-cyanuric acid complex microrods under N₂ atmosphere, which were synthesized by hydrothermal treatment of melamine solution at 180 ℃ for 24 h. The as-obtained g-C₃N₄microtubes exhibited a large surface area and a unique one-dimensional tubular structure, which provided abundant active sites for proton reduction and also facilitated the electron transfer processes. As such, the g-C₃N₄ microtubes showed enhanced photocatalytic H₂ productionactivity in lactic acid aqueous solutions under visible light irradiation (λ ≥ 420 nm), which was ~ 3.1 times higher than that of bulk g-C₃N₄ prepared by direct thermal polymerization of the melamine precursor under the same calcination conditions.