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Heterogeneous CO2 hydrogenation catalytic reactions, as the strategies for CO2 emission reduction and green carbon resource recycling, play important roles in alleviating global warming and energy shortages. Among these strategies, photothermal CO2 hydrogenation technology has become one of the hot catalytic technologies by virtue of the synergistic advantages of thermal catalysis and photocatalysis. And it has attracted more and more researchers’ attentions. Various kinds of effective photothermal catalysts have been gradually discovered, and nickel-based catalysts have been widely studied for their advantages of low cost, high catalytic activity, abundant reserves and thermal stability. In this review, the applications of nickel-based catalysts in photothermal CO2 hydrogenation are summarized. Finally, through a good understanding of the above applications, future modification strategies and design directions of nickel-based catalysts for improving their photothermal CO2 hydrogenation activities are proposed.

With the development of the world economy and the rapid advancement of global industrialization, the demand for energy continues to grow. The significant consumption of fossil fuels, such as oil, coal, and natural gas, has led to excessive carbon dioxide emissions, causing global ecological problems. CO2 hydrogenation technology can convert CO2 into high-value chemicals and is considered one of the potential ways to solve the problem of CO2 emissions. Metal/semiconductor catalysts have shown good activity in carbon dioxide hydrogenation reactions and have attracted widespread attention. Therefore, we summarize the recent research on metal/semiconductor catalysts for photocatalytic CO2 hydrogenation from the design of catalysts to the structure of active sites and mechanistic investigations, and the internal mechanism of the enhanced activity is elaborated to give guidance for the design of highly active catalysts. Finally, based on a good understanding of the above issues, this review looks forward to the development of future CO2 hydrogenation catalysts.

BiOX (X = Cl, Br, I) families are a kind of new type of photocatalysts, which have attracted the attention of more and more researchers. The suitable band gaps and their convenient tunability via the change of X elements enable BiOX to adapt to many photocatalytic reactions. In addition, because of their characteristics of the unique layered structure and indirect bandgap semiconductor, BiOX exhibits excellent separation efficiency of photogenerated electrons and holes. Therefore, BiOX could usually demonstrate fine activity in many photocatalytic reactions. In this review, we will present the various applications and modification strategies of BiOX in photocatalytic reactions. Finally, based on a good understanding of the above issues, we will propose the future directions and feasibilities of the reasonable design of modification strategies of BiOX to obtain better photocatalytic activity toward various photocatalytic applications.

Bi-based semiconductor materials have special layered structure and appropriate band gap, which endow them with excellent visible light response ability and stable photochemical characteristics. As a new type of environment-friendly photocatalyst, they have received extensive attention in the fields of environmental remediation and energy crisis resolution and have become a research hotspot in recent years. However, there are still some urgent issues that need to be addressed in the practical large-scale application of Bi-based photocatalysts, such as the high recombination rate of photogenerated carriers, limited response range to visible spectra, poor photocatalytic activity, and weak reduction ability. In this paper, the reaction conditions and mechanism of photocatalytic reduction of CO2 and the typical characteristics of Bi-based semiconductor materials are introduced. On this basis, the research progress and application results of Bi-based photocatalysts in the field of reducing CO2, including vacancy introduction, morphological control, heterojunction construction, and co-catalyst loading, are emphasized. Finally, the future prospects of Bi-based photocatalysts are prospected, and it is pointed out that future research directions should be focused on improving the selectivity and stability of catalysts, deeply exploring reaction mechanisms, and meeting industrial production requirements.

The weak adsorption of CO2 and the fast recombination of photogenerated charges harshly restrain the photocatalytic CO2 reduction efficiency. The simultaneous catalyst design with strong CO2 capture ability and fast charge separation efficiency is challenging. Herein, taking advantage of the metastable characteristic of oxygen vacancy, amorphous defect Bi2O2CO3 (named BOvC) was built on the surface of defect-rich BiOBr (named BOvB) through an in situ surface reconstruction progress, in which the CO32− in solution reacted with the generated Bi(3−x)+ around the oxygen vacancies. The in situ formed BOvC is tightly in contact with the BOvB and can prevent the further destruction of the oxygen vacancy sites essential for CO2 adsorption and visible light utilization. Additionally, the superficial BOvC associated with the internal BOvB forms a typical heterojunction promoting the interface carriers’ separation. Finally, the in situ formation of BOvC boosted the BOvB and showed better activity in the photocatalytic reduction of CO2 into CO (three times compared to that of pristine BiOBr). This work provides a comprehensive solution for governing defects chemistry and heterojunction design, as well as gives an in-depth understanding of the function of vacancies in CO2 reduction.

The pollution of phenol wastewater is becoming worse. In this paper, a 2D/2D nanosheet-like ZnTiO3/Bi2WO6 S-Scheme heterojunction was synthesized for the first time through a two-step calcination method and a hydrothermal method. In order to improve the separation efficiency of photogenerated carriers, the S-Scheme heterojunction charge-transfer path was designed and constructed, the photoelectrocatalytic effect of the applied electric field was utilized, and the photoelectric coupling catalytic degradation performance was greatly enhanced. When the applied voltage was +0.5 V, the ZnTiO3/Bi2WO6 molar ratio of 1.5:1 had highest degradation rate under visible light: the degradation rate was 93%, and the kinetic rate was 3.6 times higher than that of pure Bi2WO6. Moreover, the stability of the composite photoelectrocatalyst was excellent: the photoelectrocatalytic degradation rate of the photoelectrocatalyst remained above 90% after five cycles. In addition, through electrochemical analysis, XRD, XPS, TEM, radical trapping experiments, and valence band spectroscopy, we found that the S-scheme heterojunction was constructed between the two semiconductors, which effectively retained the redox ability of the two semiconductors. This provides new insights for the construction of a two-component direct S-scheme heterojunction as well as a feasible new solution for the treatment of phenol wastewater pollution.