Research Progress in Semiconductor Materials with Application in the Photocatalytic Reduction of CO2

The large-scale burning of non-renewable fossil fuels leads to the gradual increase of the CO2 concentration in the atmosphere, which is associated with negative impacts on the environment. The consequent need to reduce the emission of CO2 resulting from fossil fuel combustion has led to a serious energy crisis. Research reports indicate that the photocatalytic reduction of CO2 is one of the most effective methods to control CO2 pollution. Therefore, the development of novel high-efficiency semiconductor materials has become an important research field. Semiconductor materials need to have a structure with abundant catalytic sites, among other conditions, which is of great significance for the practical application of highly active catalysts for CO2 reduction. This review systematically describes various types of semiconductor materials, as well as adjustments to the physical, chemical and electronic characteristics of semiconductor catalysts to improve the performance of photocatalytic reduction of CO2. The principle of photocatalytic CO2 reduction is also provided in this review. The reaction types and conditions of photocatalytic CO2 reduction are further discussed. We believe that this review will provide a good basis and reference point for future design and development in this field.

A Critical Review on Black Phosphorus-Based Photocatalytic CO2 Reduction Application

Energy shortages and greenhouse effects are two unavoidable problems that need to be solved. Photocatalytically converting CO₂ into a series of valuable chemicals is considered to be an effective means of solving the above dilemmas. Among these photocatalysts, the utilization of black phosphorus for CO₂ photocatalytic reduction deserves a lightspot not only for its excellent catalytic activity through different reaction routes, but also on account of the great preponderance of this relatively cheap catalyst. Herein, this review offers a summary of the recent advances in synthesis, structure, properties, and application for CO₂ photocatalytic reduction. In detail, the review starts from the basic principle of CO₂ photocatalytic reduction. In the following section, the synthesis, structure, and properties, as well as CO₂ photocatalytic reduction process of black phosphorus-based photocatalyst are discussed. In addition, some possible influencing factors and reaction mechanism are also summarized. Finally, a summary and the possible future perspectives of black phosphorus-based photocatalyst for CO₂ reduction are established.

Porous Silicon Carbide (SiC): A Chance for Improving Catalysts or Just Another Active-Phase Carrier?

There is an obvious gap between efforts dedicated to the control of chemicophysical and morphological properties of catalyst active phases and the attention paid to the search of new materials to be employed as functional carriers in the upgrading of heterogeneous catalysts. Economic constraints and common habits in preparing heterogeneous catalysts have narrowed the selection of active-phase carriers to a handful of materials: oxide-based ceramics (e.g. Al₂O₃, SiO₂, TiO₂, and aluminosilicates-zeolites) and carbon. However, these carriers occasionally face chemicophysical constraints that limit their application in catalysis. For instance, oxides are easily corroded by acids or bases, and carbon is not resistant to oxidation. Therefore, these carriers cannot be recycled. Moreover, the poor thermal conductivity of metal oxide carriers often translates into permanent alterations of the catalyst active sites (i.e. metal active-phase sintering) that compromise the catalyst performance and its lifetime on run. Therefore, the development of new carriers for the design and synthesis of advanced functional catalytic materials and processes is an urgent priority for the heterogeneous catalysis of the future. Silicon carbide (SiC) is a non-oxide semiconductor with unique chemicophysical properties that make it highly attractive in several branches of catalysis. Accordingly, the past decade has witnessed a large increase of reports dedicated to the design of SiC-based catalysts, also in light of a steadily growing portfolio of porous SiC materials covering a wide range of well-controlled pore structure and surface properties. This review article provides a comprehensive overview on the synthesis and use of macro/mesoporous SiC materials in catalysis, stressing their unique features for the design of efficient, cost-effective, and easy to scale-up heterogeneous catalysts, outlining their success where other and more classical oxide-based supports failed. All applications of SiC in catalysis will be reviewed from the perspective of a given chemical reaction, highlighting all improvements rising from the use of SiC in terms of activity, selectivity, and process sustainability. We feel that the experienced viewpoint of SiC-based catalyst producers and end users (these authors) and their critical presentation of a comprehensive overview on the applications of SiC in catalysis will help the readership to create its own opinion on the central role of SiC for the future of heterogeneous catalysis.

0D/2D Heterojunctions of Ti3C2 MXene QDs/SiC as an Efficient and Robust Photocatalyst for Boosting the Visible Photocatalytic NO Pollutant Removal Ability

In this work, a novel heterojunction catalyst was constructed by introducing Ti₃C₂ MXene quantum dots (QDs) into SiC. The Ti₃C₂ MXene QDs/SiC composite showed 74.6% efficiency in NO pollutant removal under visible light irradiation, which is 3.1 and 3.7 times higher than those of the bare Ti₃C₂ MXene quantum dots and SiC, respectively. The Ti₃C₂ MXene quantum dots existing in SiC can function as a channel for electron and hole transfer. The enhanced visible light absorption, increased superoxide radical, and strong oxidization ability endow the Ti₃C₂ MXene QDs/SiC composite with a superior photocatalytic performance for NOx removal. The increased superoxide radical formation and enhanced oxidization ability of Ti₃C₂ MXene QDs/SiC were demonstrated by theoretical calculations. The robust stability in both photocatalytic performance and crystal structures was revealed in the Ti₃C₂ MXene QDs/SiC composite using the cycling test, transient photocurrent response, XRD, and TG.

Highly efficient photocatalytic reduction of CO2 to CO using cobalt oxide-coated spherical mesoporous silica particles as catalysts

Hybrid catalysts that cobalt oxide nanoparticles immobilized on outside surfaces of spherical SBA-15 presented unexpected photocatalytic activity towards CO₂-to-CO conversion.