The transformation of CO into fuels and chemicals by photocatalysis is a promising strategy to provide a long-term solution to mitigating global warming and energy-supply problems. Achievements in photocatalysis during the last decade have sparked increased interest in using sunlight to reduce CO . Traditional semiconductors used in photocatalysis (e.g. TiO ) are not suitable for use in natural sunlight and their performance is not sufficient even under UV irradiation. Some two-dimensional (2D) materials have recently been designed for the catalytic reduction of CO . These materials still require significant modification, which is a challenge when designing a photocatalytic process. An overarching aim of this Review is to summarize the literature on the photocatalytic conversion of CO by various 2D materials in the liquid phase, with special attention given to the development of novel 2D photocatalyst materials to provide a basis for improved materials.

”Systematic errors”, namely, oxygen vacancy sites in ZnO, are the active centers for the hydrogenation of CO to give methanol. Nanocrystalline ZnO with a high density of oxygen vacancies was prepared from special organometallic precursors, and its catalytic properties for methanol synthesis were studied.

Is this place taken? A mechanism has been proposed for the formation of methanol from CO and H2 on ZnO surfaces in which CO is adsorbed at oxygen vacancies on the heterogeneous catalyst (see picture: C red, H white, O gray, Zn black). The active sites are blocked when CO2 is added to the gas mixture.

We investigated photoelectrodes based on TiO(2)-polyheptazine hybrid materials. Since both TiO(2) and polyheptazine are extremely chemically stable, these materials are highly promising candidates for fabrication of photoanodes for water photooxidation. The properties of the hybrids were experimentally determined by a careful analysis of optical absorption spectra, luminescence properties and photoelectrochemical measurements, and corroborated by quantum chemical calculations. We provide for the first time clear experimental evidence for the formation of an interfacial charge-transfer complex between polyheptazine (donor) and TiO(2) (acceptor), which is responsible for a significant red shift of absorption and photocurrent response of the hybrid as compared to both of the single components. The direct optical charge transfer from the HOMO of polyheptazine to the conduction band edge of TiO(2) gives rise to an absorption band centered at 2.3 eV (540 nm). The estimated potential of photogenerated holes (+1.7 V vs. NHE, pH 7) allows for photooxidation of water (+0.82 V vs. NHE, pH 7) as evidenced by visible light-driven (λ > 420 nm) evolution of dioxygen on hybrid electrodes modified with IrO(2) nanoparticles as a co-catalyst. The quantum-chemical simulations demonstrate that the TiO(2)-polyheptazine interface is a complex and flexible system energetically favorable for proton-transfer processes required for water oxidation. Apart from water splitting, this type of hybrid materials may also find further applications in a broader research area of solar energy conversion and photo-responsive devices.

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Photocatalytic CO2 reduction to produce valuable chemicals and fuels using solar energy provides an appealing route to alleviate global energy and environmental problems. Searching for photocatalysts with high activity and selectivity for CO2 conversion is the key to achieving this goal. Among the various proposed photocatalysts, metal‐free materials, such as graphene, nitrides, carbides, and conjugated organic polymers, have gained extensive research interest for photocatalytic CO2 reduction, due to their earth abundance, cost‐effectiveness, good electrical conductivity, and environmental friendliness. They exhibit prominent catalytic activity, impressive selectivity, and long durability for the conversion of CO2 to solar fuels. Herein, the recent progress on metal‐free photocatalysis of CO2 reduction is systematically reviewed. Opportunities and challenges on modification of nonmetallic catalysts to enhance CO2 transformation are presented. Theoretical calculations on possible reduction mechanisms and pathways as well as the potential in situ and operando techniques for mechanistic understanding are also summarized and discussed. Based on the aforementioned discussions, suitable future research directions and perspectives for the design and development of potential nonmetallic photocatalysts for efficient CO2 reduction are provided.

A systematic series of binary and ternary copper catalysts was investigated using the methanol synthesis reaction at atmospheric pressure. Strong metal-support interactions between copper and zinc oxide induced by strongly reducing conditions were probed by the adsorption of carbon monoxide, which was monitored qualitatively and quantitatively by a combination of microcalorimetry, temperature-programmed desorption experiments and Fourier transform infrared spectroscopy. For the zinc oxide-containing catalysts, the pretreatment in flowing carbon monoxide at 493 K resulted in a severe decoration of the copper metal particles with ZnOx adspecies, whereas after methanol synthesis at 493 K the state of the copper was essentially identical to that seen after hydrogen reduction. Copper was always found to be present in its zero-valent state.

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