Artificial Trees for Artificial Photosynthesis: Construction of Dendrite-Structured α-Fe₂O₃/g-C₃N₄ Z-Scheme System for Efficient CO₂ Reduction into Solar Fuels

Abstract

A direct all-solid-state Z-scheme heterojunction photocatalyst of a g-C3N4-coated tree-like α-Fe2O3 was rationally constructed toward CO2 conversion. The so-called artificial tree shows excellent performance and stability for CO production (17.8 μmol g–1 h–1), almost 3 times that of pristine g-C3N4. Density functional theory computations explain the intrinsic cause for the formation of the Z-scheme structure. The enhanced photocatalytic performance can be attributed to a synergistic effect of the following factors: (1) the combination of α-Fe2O3 with g-C3N4 helps to promote light harvesting and CO2 adsorption; (2) the hybridization effectively enhances the spatial separation of photogenerated electrons and holes, suppressing the undesirable recombination of charge carriers; (3) the dendritic structure of α-Fe2O3 provides ample active sites with considerable steps, edges, and kinks along the twigs, and meanwhile, the exposed (001) facet with high electron conduction facilitates photoelectrons’ transportation to the interface. This work provides new insight into constructing Z-scheme photocatalysts for CO2 conversion.

Recent Advances in Surface-Modified g-C₃N₄-Based Photocatalysts for H₂ Production and CO₂ Reduction

“…The use of sunlight for overall water splitting is considered to be a major chemical challenge. According to the thermodynamic requirements, the CB potential of photocatalyst must be more negative than the potential of H + /H2, while the valence band (VB) potential must be more positive than the potential of O2/H2O 6 . For example, the CB position of g-C3N4 usually locates at −1.1 eV, thus it is more negative than the hydrogen production potential.…”

“…As a result, this double Z-scheme heterojunction acquires a high-efficient conversion of CO2 molecules into various solar fuels such as CO, CH4, CH3OH and CH3CH2OH, and the conversion rate of hydrocarbon fuel is highly up to 91.5%. The various g-C3N4based Z-scheme heterojunctions for photocatalytic CO2 reduction and H2 production reported in the recent years are listed in the Table 2 6,8,[117][118][119][123][124][125][126] .…”

“…The renewable energy technologies should be developed to address the global warming caused by carbon dioxide from fossil fuel consumption and to build a sustainable society [1][2][3][4][5] . Solar energy, as the largest renewable energy of the world, is the primary energy source of wind energy, tidal energy, biomass energy and fossil fuel [6][7][8][9][10] . Photocatalysis technology is a sunlight-driven chemical reaction process on the surface of photocatalysts that can generate H2 from water [11][12][13][14] , decompose organic contaminants [15][16][17] , photocatalytic sterilization [18][19][20] and reduce CO2 into organic fuels [21][22][23][24] .…”

Synthesis and Characterization of an α-Fe2O3-Decorated g-C3N4 Heterostructure for the Photocatalytic Removal of MO

“…Therefore, two-component g-C 3 N 4 based systems are synthesized to form heterojunction structures with a higher photocatalytic efficiency utilizing a wide wavelength range [19]. Thus far, various reports have published the Z-scheme action and heterojunction mechanism of the g-C 3 N 4 /α-Fe 2 O 3 composite in pollutant degradation [20], CO 2 reduction [21][22][23], photoelectrochemical [24,25], Hg (II) reduction [26], etc. However, there are few reports comprising the ternary and quaternary systems of g-C 3 N 4 /α-Fe 2 O 3 for the degradation of wastewater dyes following the heterojunction mechanism [20].…”

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

“…For example, TiO 2 has been considered as one of the most popular semiconductors applied to photocatalysis with prestigious advantages, including easy availability, low toxicity, outstanding chemical stability, and unique optical and electronic properties, and a recently published review on TiO 2 ‐based photocatalysts for CO 2 reduction is available 54 . Nevertheless, because of inefficient solar energy utilization substantiated by the wide bandgap, researchers have employed various methods to improve the activity of such photocatalysts, including metal or non‐metal doping, 40,41,55‐61 alloying, 42,51‐53 facet engineering, 62‐65 nanostructure tailoring, 13,40,46,66,67 surface defect engineering, 43,68,69 and p‐n heterojunction or Z‐scheme system constructing 44,45,47‐50,70‐74 . In general, these methods all aim at either improving the separation efficiency of photogenerated electron/hole pairs, namely prolonging the lifespan of electrons for CO 2 reduction, or creating more catalytically active sites.…”