Engineering approach toward catalyst design for solar photocatalytic CO ₂ reduction: A critical review

Abstract

Summary Solar‐driven converting CO2 to value‐added chemicals can not only address the ever‐growing energy crisis, but also simultaneously mitigate CO2 emission. Although much progress has been made in the last decade, it still remains great challenge to achieve the efficient reduction of CO2 with desirable productivity and high product selectivity because CO2 is a thermodynamically stable and inert molecule with large bond energy. Design and synthesis of efficient catalyst play a pivotal role in promoting the activity and selectivity of photocatalytic CO2 reduction. Apart from the active sites engineering, manipulation of the charge separation and light harvesting efficiency or prolonging the lifetime of photogenerated carriers also greatly matters. Consequently, this review summarizes recent advances in photocatalyst design for CO2 conversion from two major aspects, namely active sites engineering and carriers lifespan prolonging. Firstly, we sort out the fundamental principles and merits of artificial photosynthesis in order to provide readers with a current snapshot of this rapidly developed field. Subsequently, various catalyst engineering strategies, including doping, alloying, Z‐scheme structure construction, are discussed in detail. Finally, some challenging issues as well as insights into the future development of artificial photosynthesis are presented.

Single‐Atom Catalysts (SACs) for Photocatalytic CO2 Reduction with H2O: Activity, Product Selectivity, Stability, and Surface Chemistry

“…Inefficient charge separation or the rapid recombination of charges is a severe challenge in photocatalytic processes, leading to low catalytic activity. [70,71] These phenomena are related to the nature of the catalysts used in the reaction. Two types of semiconducting catalysts are typically used, namely, i) wide bandgap semiconductors (e.g., TiO 2 and ZnO) and ii) narrow bandgap semiconductors (e.g., Cu 2 O and MoS 2 ).…”

“…Therefore, photocatalytic CO 2 reduction is achieved by combining the reactant (i.e., CO 2 ), photocatalyst, proton source (e.g., H 2 O), and light source under appropriate reaction conditions. [ 70 ] First, the catalyst absorbs light of equal or higher energy than its bandgap throughout the reduction process, creating electron–hole pairs. The valence band (VB) electrons are excited to the conduction band (CB), leaving holes in the VB.…”

Photocatalytic CO2conversion: from C1 products to multi-carbon oxygenates

“…The typical process of photocatalytic CO 2 reduction on semiconductor photocatalysts mainly consists of four steps: light absorption, charge separation, CO 2 adsorption, and redox reactions. 17,18 The first step of a photocatalyst is to absorb photons from sunlight to produce electrons and holes on the conduction band (CB) and valence band (VB), respectively, which serve as reductant and oxidant in photocatalytic reactions. In order to reduce CO 2 molecules, the suitable band structure of photocatalysts is strictly demanded.…”

Rational Design and Application of Covalent Organic Frameworks for Solar Fuel Production

“…The Re-bpy-COF with bipyridine units exhibited second highest reaction rate due to the extended conjugation offered by the Re complex. According to the recently reported studies, the state-of-the-art photocatalysts for CO 2 reduction also displays comparable activity to the COF materials [ 83 , 84 ]. Table 8 summarizes some of the photoactive materials including Ag-Cr/Ga 2 O 3 (CO, 480 µmolg −1 h −1 ) [ 85 ], Cu@V-TiO 2 /PU (CH 4 , 933 µmolg −1 h −1 ) [ 86 ], ZnO nanosheets (CO, 406.77 µmolg −1 h −1 ) [ 87 ], Rh-Au-SrTiO 3 (CO, 369 µmolg −1 h −1 ) [ 88 ], Mo-doped g-C 3 N 4 (CO, 887 µmolg −1 h −1 ) [ 89 ] and Nb-TiO 2 /g-C 3 N 4 (CH 4 , 562 µmolg −1 h −1 ) [ 90 ].…”