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Photocatalysts for efficient solar hydrogen production are highly sought after. Here a new type of nitrogen‐doped tantalum tungstenate (CsTaWO6) material, which demonstrates excellent visible light absorption and improved photocatalytic activity, is demonstrated. X‐ray diffraction (XRD) patterns reveal that the defect pyrochlore‐type structure of CsTaWO6 remained intact upon nitrogen doping. UV‐vis spectra indicate that nitrogen doping in the compound results in a red‐shift of the absorption edge from 358 nm to 580 nm, thus offering significantly increased visible light absorption. X‐ray photoelectron spectroscopy (XPS) further indicates that [Ta/W]–N bonds were formed by inducing nitrogen to replace a small amount of oxygen in the material, resulting in a compound of CsTaWO6‐xNx. The explanation of the experimental results is supported by density functional theory calculations. The density of states (DOS) and the projected DOS after substitutional doping of nitrogen in CsTaWO6 indicated that N‐doping reduces the bandgap significantly from 3.8 to 2.3 eV due to N 2p and O 2p orbital mixing. The role of the new N 2p states is also investigated by studying the production of the •OH radicals in the visible light region (>420 nm). In CsTaWO6‐xNx, the N 2p orbitals are the main contributors to the top of the valence band, causing bandgap narrowing while the bottom of conduction band, due to Ta 4d orbitals, remains almost unchanged. Compared with its undoped counterpart, nitrogen‐doped CsTaWO6‐xNx exhibits a nearly 100% increase in solar hydrogen production efficiency.

AbstractFormaldehyde is one of the most important intermediate chemicals and has been produced industrially since 1889. Formaldehyde is a key feedstock in several industries like resins, polymers, adhesives, and paints, making it one of the most valuable chemicals in the world. However, not many studies have been dedicated to reviewing the production of this economically important product. In this review paper, we study the leading commercial processes for formaldehyde production and compare them with recent advancements in catalysis and novel processes. This paper compares, in extensive detail, the reaction mechanisms and kinetics of water ballast process (or BASF process), methanol ballast process, and Formox process. The thermodynamics of the reactions involved in the formaldehyde production process was investigated using HSC Chemistry™ software (Outotec Oyj, Espoo, Finland). Exergy analysis was carried out for the natural gas to methanol process and the methanol ballast process for formaldehyde production. The former process was simulated using Aspen HYSYS™ and the latter using Aspen Plus™ software (Aspen technology, Burlington, MA, USA). The yield and product specifications from the simulation results closely matched with published experimental data. The exergy efficiencies of the natural gas to synthesis gas

Discovery of a low temperature route to produce formaldehyde via catalytic hydrogenation of carbon monoxide in the aqueous phase.

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