CO2 Photoconversion Research Articles

Visible light driven photocatalytic reduction of CO2 on Au-Pt/Cu2O/ReS2 with high efficiency and controllable selectivity

Photocatalytic conversion of CO2 to value-added chemicals and fuels is a green and sustainable approach to solve the problems of CO2 concentration increment and fossil fuels shortage. Employing photocatalysts with high catalytic activity and selectivity to realize CO2 conversion has attracted extensive attention. However, the efficiency of photocatalysts is still unsatisfied and the selectivity of products is hard to be regulated, hindering their practical applications in large scale commercial purpose. In this work, for the first time, the Au and Pt was co-deposited on the heterostructure consisted of Cu2O quantum dots and ReS2 nanosheets to achieve high efficiency and controllable selectivity during CO2 photoreduction. The Au-Pt/Cu2O/ReS2 photocatalysts show superior efficiency of CO2 reduction than that of Au/Cu2O/ReS2, Pt/Cu2O/ReS2, Cu2O/ReS2, Cu2O. Such distinct improvement is attributed to the indirect Z-scheme mechanism and Schottky junction effect. Moreover, the synergetic effect of Au and Pt plays an important role of improving the photocatalytic activity, and the Au1-Pt5/Cu2O/ReS2 exhibits the highest Relectron of 516.86 μmol/g during one hour of visible light illumination, which is much larger than many recently reported photocatalysts under comparable condition. Meanwhile, the selectivity of CO and CH4 is effortlessly tunable from 0 to 100% by modulating Au/Pt metal mass ratio due to the strong CO adsorption on Pt metals and the intensive interaction between Au and Pt atoms at the Au/Pt interface. This controllable selectivity provides admirable strategy to tune the component proportion of the gas products for the subsequent conversion into high value-added chemicals or liquid fuels. Our study proposes novel and deep insights into the design and fabrication of practical photocatalysts with high catalytic activity and controllable selectivity to perform efficient CO2 photoconversion.

Influence of TiO2 dispersion on silica support toward enhanced amine assisted CO2 photoconversion to methanol

In this work, titania-supported fibrous silica (TiO2-KCC1) and Fibrous Silica-Titania (FST) were prepared via microemulsion technique with a different sequence of titania incorporation method. The catalysts were characterized by x-ray diffraction (XRD), N2 adsorption-desorption, field emission scanning electron microscopy (FESEM), transmission electron microscopes (TEM), and fourier-transform infrared spectroscopy (FTIR). The results discovered that the FST catalyst had high crystallinity, higher specific surface area, and large pore volume. The alternate arrangement of TiO2 and silica in the framework of fibrous silica on FST catalyst had an excellent dispersion and it triggered stronger TiO2–SiO2 interactions. It was observed that in the absence of triethylamine (TEA), formic acid (HCOOH) was much favourable produced by both catalysts, with the highest HCOOH product was obtained using TiO2/KCC-1 (2933 µmol/gcat.h). In the presence of TEA as a sacrificial agent, superior methanol production was perceived using FST (3487 µmol/gcat.h) as compared to TiO2/KCC-1 (2773 µmol/gcat.h). It was proposed that the unique structure of the FST catalyst absorbed many photons and was able to absorb more carbon dioxide (CO2) molecules onto the active site of the catalyst to produce carbonic acid (H2CO3) active radicals. With the assist of TEA, methanol production drastically boosts up almost three times higher than the absence of TEA, probably due to an excess of electrons leading to the formation of more active radicals, thus enhancing the methanol production. The response surface methodology (RSM) result indicated that the utmost yield could be obtained at catalyst dosage 0.619 g/L, TEA volume 157.24 µL, and CO2 flow rate 9.47 mL/min. The experimental validation of the predicted optimum condition revealed that the methanol yield is 3062.966 mol g−1 h−1, compared to the predicted value of 3026.95 mol g−1 h−1, with only a 1.18% difference.

Artificial photosynthesis using ultrathin 2D materials

Ultrathin 2D nano materials are gaining enormous attention after Geim and co-worker reported graphene from mechano-chemical exfoliation of ordered graphite. The extraordinary optoelectronic and physico-chemical properties of ultrathin 2D nanomaterials owing to its unistructural features offer diversified applications. Artificial photosynthesis is a mimic process of natural photosynthesis that include a photocatalyst to fix and convert CO2 to clean fuel. Ultrathin 2D nano materials furnishes high active sites with maximum edge and interface area that determine the CO2 photo-conversion efficiency and selectivity. Here in, we have reported the summaries of synthesis, co-catalytic behavior, CO2 conversion efficiency and selectivity of ultrathin 2D nanomaterials for energy generation and fine chemical transformation. Graphene and its analogous i.e. Transition Metal Di-chalcogenides (TMDS), graphitic Carbon Nitrides (g-C3N4), Metal Organic frameworks (MOF), Covalent Organic Frameworks (COF), MXenes, Layered Double Hydroxides (LDH), Black Phosphorus (BP) and metal oxides like RuO2/TiO2, etc. are categorized for photo-conversion of CO2. Nanostructured geometry and higher active surface area of nanocatalysts are focused for the selective CO2 conversion.

Solar‐powered chemistry: Engineering low‐dimensional carbon nitride‐based nanostructures for selective CO2 conversion to C1C2 products

AbstractCO2 capture and conversion has been prospected as an auspicious technology to simultaneously tackle the rise in global CO2 emission and produce value‐added fuels with the goal of accomplishing carbon neutrality. A sustainable route to achieve this is via the utilization of solar energy, thereby harnessing the abundant and nonexhaustive resource to shift our reliance away from rapidly depleting fossil fuels. Graphitic carbon nitride (g‐C3N4) and its allotrope have earned its rank as a fascinating metal‐free photocatalyst due to its superior stability, high surface‐area‐to‐volume ratio, and tunable surface engineering. By leveraging these properties, robust carbon nitride‐based nanostructures are engineered for photocatalytic CO2 conversion to energy‐rich C1C2 product, which is indispensable in the chemical industry. Thus, this review presents the latest panorama of experimental and computational research on tuning the local electronic, surface chemical coordination environment, charge dynamics and optical properties of low‐dimensional carbon nitride and its allotropes toward highly selective and efficient CO2 photoconversion. To name a few, structural engineering, point‐defect engineering, heterojunction construction, and cocatalyst loading. To advance this frontier, critical insights are elucidated to establish the structure‐performance relationship and unravel primary factors dictating the selectivity of C1C2 molecules from CO2 reduction. External‐field assisted photocatalysis such as with electric (photoelectro‐) and heat (photothermal) is discussed to uncover the synergistic contributions that drive the development in photochemistry. Last, future challenges and prospects are outlined for the potential application of solar‐driven CO2 conversion, along with the scale‐up strategy from the economic viewpoint toward the rational development of high‐efficiency carbon nitride catalysts. image

Understanding rich oxygen vacant hollow CeO2@MoSe2 heterojunction for accelerating photocatalytic CO2 reduction

Solar-driven CO2 reduction into gas fuels is desirable for a sustainable carbon cycle. To improve the photocatalytic activity of CO2RR, the unique rich oxygen (Vo) vacant hollow CeO2@MoSe2 is designed. The introduction of Vo is conducive to the capture of electrons by CO2 and promotes the process of photocatalytic CO2RR. The heterojunction formed by introducing the narrow band gap semiconductor MoSe2 increases the absorption range of visible light and improves the separation efficiency of photogenerated carriers. The hollow structure improves the CO2 adsorption capacity and improves the use of light effect. Therefore, the prepared H-Vo-CeO2@49.7 wt% MoSe2 exhibits enhanced photocatalytic activity for CO2RR. The yield of CH4 and CO is 10.2 µmol and 33.2 µmol in 4 h. Moreover, the photocatalytic mechanism is discussed through DFT and in-situ DRIFTS. This work provides new insights to the role of Vo in active CO2 photoconversion and exploits an important application of CO2 reduction.

Preparation and Application of Nb2O5 Nanofibers in CO2 Photoconversion.

Increasing global warming due to NO, CO, and CH, is significantly harming ecosystems and life worldwide. One promising methodology is converting pollutants into valuable chemicals via photocatalytic processes (by reusable photocatalysts). In this context, the present work aimed to produce a NbO photocatalyst nanofiber system by electrospinning to convert CO. Based on the collected data, the calcination at 600 C for 2 h resulted in the best condition to obtain nanofibers with homogeneous surfaces and an average diameter of 84 nm. As a result, the NbO nanofibers converted CO mostly into CO and CH, reaching values around 8.5 mol g and 0.55 mol g, respectively.

Biomolecule assisted hydrothermal synthesis of indium intercalated 2D ZrSe2 microflowers for photocatalytic CO2 reduction to MeOH and CH4

Indium (In)-intercalated zirconium diselenide (InZrSe2) microflowers were prepared through solvothermal method assisted with alginic acid biomolecule. The In intercalation into 2D ZrSe2 nanostructures helped for the nucleation process along with cationic stability and improved crystallinity as well as morphology. The InZrSe2 microflowers have optimized bandgap value i.e., 1.65 eV and showed good photocatalytic CO2 conversion to methanol and methane through hydrogenation. The results showed satisfied selectivity for methanol (87%) during CO2 photoconversion with production rate up to 740.574µmolg-1h−1 and rate of methane hydrogenation (54% selectivity) to be 10.12µmolg-1h−1. Also, the photocatalytic degradation of Congo red (CR) was observed up to 86% for 10 ppm solution.

Energy Band Alignment and Redox-Active Sites in Metalloporphyrin-Spaced Metal-Catechol Frameworks for Enhanced CO2 Photoreduction.

Two new chemically stable metalloporphyrin-bridged metal-catechol frameworks, InTCP-Co and FeTCP-Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers. The CO2 photoreduction rate over FeTCP-Co considerably exceeds that obtained over InTCP-Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron-oxo coordination chain assists energy band alignment and provides a redox-active site, and the uncoordinated hydroxyl group contributes to the visible-light absorptance, charge-carrier transfer, and CO2 -scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP-OH-Co affords CO2 photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP- Co and InTCP-Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation.

Energy Band Alignment and Redox‐Active Sites in Metalloporphyrin‐Spaced Metal‐Catechol Frameworks for Enhanced CO2 Photoreduction

AbstractTwo new chemically stable metalloporphyrin‐bridged metal‐catechol frameworks, InTCP‐Co and FeTCP‐Co, were constructed to achieve artificial photosynthesis without additional sacrificial agents and photosensitizers. The CO2 photoreduction rate over FeTCP‐Co considerably exceeds that obtained over InTCP‐Co, and the incorporation of uncoordinated hydroxyl groups, associated with catechol, into the network further promotes the photocatalytic activity. The iron‐oxo coordination chain assists energy band alignment and provides a redox‐active site, and the uncoordinated hydroxyl group contributes to the visible‐light absorptance, charge‐carrier transfer, and CO2‐scaffold affinity. With a formic acid selectivity of 97.8 %, FeTCP‐OH‐Co affords CO2 photoconversion with a reaction rate 4.3 and 15.7 times higher than those of FeTCP‐ Co and InTCP‐Co, respectively. These findings are also consistent with the spectroscopic study and DFT calculation.

Dual modulation steering electron reducibility and transfer of bismuth molybdate nanoparticle to boost carbon dioxide photoreduction to carbon monoxide

Owing to the exorbitant CO2 activation energy and unsatisfactory photogenerated charge separation efficiency, CO2 photoconversion still faces enormous challenges. In this study, a directional electron transfer channel has been established by decorating N-doped carbon quantum dots (N-CQDs) on the surface of Bi4MoO9 nanoparticles to ensure that more active electrons can participate in the CO2 reduction. The conduction band of Bi4MoO9 nanoparticles is calculated to be −1.55 eV versus the normal hydrogen electrode (NHE), pH = 7, which is negative enough to attain the photocatalytic CO2 reduction potential of −0.53 eV versus NHE, pH = 7. CO2 adsorption curves and in situ Fourier transform infrared spectra reveal that N-CQDs facilitate surface CO2 adsorption and activation, as well as CO desorption. In addition, steady-state photoluminescence and photoelectrochemical tests prove that the charge separation efficiency can be greatly enhanced by constructing N-CQDs/Bi4MoO9 composites. In the presence of pure water, N-CQDs/Bi4MoO9-2 composite achieved a CO yield of 16.22 μmol g−1 after 5 h Xe light illumination, which was 3.24 times higher than that of pure Bi4MoO9 (4.98 μmol g−1). This study offers a distinctive approach to the optimization of Bi4MoO9 photocatalysts and their application in energy conversion.

Assembling an Affinal 0D CsPbBr3/2D CsPb2Br5 Architecture by Synchronously In Situ Growing CsPbBr3 QDs and CsPb2Br5 Nanosheets: Enhanced Activity and Reusability for Photocatalytic CO2 Reduction.

Conversion of CO2 into valuable chemical feedstocks through artificial photosynthesis is an effective strategy to alleviate energy and environmental issues. Herein, we have developed a novel perovskite-based catalyst via in situ growing CsPbBr3 quantum dots (QDs) on the affinal 2D CsPb2Br5 nanosheets for CO2 photoconversion. CsPbBr3 QDs were generated by peeling off layers from their cubic counterpart; meanwhile, CsPb2Br5 nanosheets were formed by heaping up the peeled layers. The resultant dual-phase composite exhibited outstanding activity and selectivity for photocatalytic conversion of gaseous CO2 with a CO generation rate of 197.11 μmol g-1 h-1 under 300 W Xe lamp irradiation, which is 2.5 and 1.1 times higher than that of pure CsPb2Br5 or CsPbBr3. Importantly, the fabricated dual-phase material presented extremely high stability and was able to maintain an unchangeable CO2 conversion rate under wet air in the consecutive 10 h of recycling test. Furthermore, attributing to the in situ assembling strategy, the close contact allowed photo-generated electrons in CsPbBr3 QDs to transfer rapidly to CsPb2Br5, and the affluent active sites in such an architecture enabled achieving enhanced CO2 photoconversion activity. The present work provides an attractive approach for in situ constructing a consubstantial perovskite-based composite photocatalyst to ensure great stability and excellent activity for artificial photocatalytic CO2 conversion.

Rational design of three-dimensional nickel borate/graphene nanoarrays for boosted photoconversion of anthropogenic CO2

Direct photoconversion of diluted CO2 into solar fuels has theoretically and practically become a hot research topic. However, the low yields and poor selectivity of carbonaceous products hampered by the H2 evolution reaction is still a challenge for its practical application. Herein, we demonstrate a three-dimensional (3D) nickel borate/graphene nanoarrays (Ni-Bi/G) for diluted CO2 photoreduction with boosted activity and selectivity. In simulated flue gas with 10% CO2, the pristine Ni-Bi displays a low activity and low CO selectivity of 41.8%, indicating its tendency of producing H2 in diluted CO2. However, after growing Ni-Bi nanoarrays onto graphene nanosheets, the optimized 3D Ni-Bi/G exhibits a high CO selectivity of 84.9% with a CO production rate of 5.1 μmol h−1, which is about 2 times of the blank sample. The improved performance can be attributed to the synergistic effect of the introduction of rGO and unique 3D structure, which are conducive not only to accelerate the separation of photogenerated charges, but also to enrich active sites and enhance CO2 adsorption. This work provides fundamental guidance to the rational design of well-designed hierarchical catalysts for photoconversion of low concentration CO2.

Organic terpyridine molecule as an efficient cocatalyst for metal–free CO2 photoreduction mediated by mesoporous graphitic carbon nitride

Metal-free catalytic conversion of CO2 with high selectivity and efficiency is promising for achieving carbon neutrality. However, nonmetallic catalytic sites for highly selective and efficient CO2 photoconversion are still challenging. In this work, organic terpyridine molecules are developed as highly active cocatalysts for visible-light-driven CO2 reduction with a CO evolution rate of 1.92 × 104 μmol g−1h−1 and 99.8% selectivity in aqueous solution, which is among the highest CO evolution rates for metal-free CO2 photoreduction. Mechanistic studies revealed that efficient electron transfer from organic light-absorbing photosensitizer to terpyridine molecules was mediated by mesoporous g-C3N4 (mpg-C3N4), with no need of much efforts to optimize inherent fast charge recombination of pristine mpg-C3N4. The synergistic effect of mpg-C3N4 and terpyridine molecule suppressed H2 evolution process from CB of mpg-C3N4 and promoted CO2 reduction at terpyridine sites. These results pave a feasible way to achieve robust metal-free CO2 photoreduction by employing organic molecular hybrid photocatalysis.

Highly Dispersed Pt Nanoparticle-Doped Mesoporous ZnO Photocatalysts for Promoting Photoconversion of CO2 to Methanol.

Photoreduction of CO2 is considered a challenge due to the lack of effective photocatalysts with wide-spectrum absorption, active charge separation dynamically, and CO2 adsorption. Herein, mesoporous Pt/ZnO nanocomposites with different Pt percentages (0.5–2%) have been fabricated using the sol–gel process in the presence of a template for CO2 photoreduction during visible-light exposure. Pt nanoparticles (NPs) deposited onto mesoporous ZnO with a considerable surface area can effectively promote charge mobility. The mesoporous 1.5% Pt/ZnO nanocomposite exhibits an optimal CH3OH yield (668 μmol g–1), which is 18.5-fold larger than that of mesoporous ZnO (36 μmol g–1). The most photoactive material was the 1.5% Pt/ZnO nanocomposite, producing CH3OH of 668 μmol g–1, and the production rate of CH3OH over the 1.5% Pt/ZnO nanocomposite (74.11 μmol g–1 h–1) was increased 20 times in comparison with ZnO NPs (3.72 μmol g–1 h–1). The enhancement of CO2 photoreduction efficiency over Pt/ZnO nanocomposites was attributed to the formation of the heterojunction at the Pt/ZnO interface, promoting a lower resistance to charge transfer and a larger electron transfer to the conduction band. Mesoporous Pt/ZnO nanocomposites offer enhanced accessibility and a larger surface area. Such an unparalleled mesostructure provides a new framework for the construction and design of photoactive materials with high-efficiency photocatalysts.

Comparisons of visible-light driven photocatalytic CO2 conversion performances over mesoporous CdSxSe1–x with different molecular compositions

This study presents a synthesis method for nanowire arrayed mesoporous CdSxSe1-x compounds with different S/Se molar ratios. Both ternary and binary compound semiconductors are synthesized by hard-templating using SBA-15 as a silica template. The synthesized mesoporous materials have high specific surface areas of approximately 65–100 m2 g−1 and remarkable light absorption properties in the UV to visible light region (1.7–2.4 eV), and thus they are appropriate for the photo-conversion of CO2 into CO and CH4. The results show that the compositions of CdSxSe1-x excellently agree with the compositions of the reactants. Moreover, the band gaps of the mesoporous CdSxSe1-x samples could be directly tuned by varying the composition of the reactants. It is concluded that mesoporous CdSe achieves the highest CH4 yield rate, i.e., 0.382 μmol gcat–1 h–1, and CdS0.5Se0.5 achieves the highest CO yield rate (among all the samples synthesized), i.e., 5.633 μmol gcat–1 h–1. Also, it is found that the CO2 photoconversion performance on mesoporous II-VI photocatalyst are highly affected by CO2 adsorption capacities and photo-generated charge separation.

Construction of hierarchical ZnS@ZnO secured from metal – organic framework- ZnS@ZIF-8 for enhanced photoreduction of CO2

BackgroundThe CO2 photochemical conversion reaction has received attention under mild conditions. The CO2 photoreduction to CH3OH has become an approach of “one stone to kill two birds” since it provides the probability to complete the carbon circle and create invaluable products in a rotational economy. MethodOne-pot synthesis of porous ZnS@ZnO was developed with a large surface area of 1530 m2/g by Zn(NO3)2, Na2S and 2-methylimidazole as precursors. The obtained Pt/ZnS@ZnO heterostructure was evaluated for photoconversion of CO2 to CH3OH through visible light illumination. Significant findingsThe most photoactive 1%Pt/ZnS@ZnO showed a CH3OH formation of 1402 µmol g−1 after 9 h, which was enhanced 11.2- and 10.97- times larger than ZnO and ZnS@ZnO. The CH3OH formation rate over 1%Pt/ZnS@ZnO was promoted 12 times greater than ZnO and ZnS@ZnO heterostructure. The synthesized photocatalyst exhibited high stability and durability after five repeated cycles within 45 h. The superior CO2 reduction over Pt/ZnS@ZnO could be imputed to i) the construction of heterojunction between ZnS and ZnO, which enhanced the charge carriers-migration process and promoted the charge carriers lifetime; ii) the different energy levels led the high oxidative ability of the adsorbed OH‾ surface and hence facilitates the catch of photoinduced holes.

A Superficial Intramolecular Alignment of Carbon Nitride through Conjugated Monomer for Optimized Photocatalytic CO2 Reduction

One of the most frequent ways to widen the adsorption range of carbon nitride (CN) is to add a well-known photosensitizer into its basic structure. So far, such attachments have been accomplished by using weak van der Waals forces. However, using strong covalent bonding to attach such photosensitizer with CN is yet to be determined. Here, for the first time, we covalently bonded porphyrin (5,10,15,20-tetrakis(4-(2,4-diamino-1,3,5-triazinyl) phenyl)-Porphyrin (TDP)), a renowned photosensitizer, effectively with CN by thermally balanced molecular strategy. A photoreaction system was set up for the deoxygenated conversion of CO2 to CO under visible light, where cobalt acted as a redox controller to speed up the charge transportation, while CN-TDP worked as a CO2 activating photocatalyst. The subsequent photocatalyst has a broader absorbance range, a greater specific surface area, and intramolecular organic connections that help to decrease the electron-hole pairs’ recombination rate. Furthermore, the average weight ratio between urea and TDP was well-tuned, resulting in a fantastic CO2 photoconversion for CN-TDP7.0 compared to the blank sample. This substantial increase in photocatalytic activity predicts a significant shift in CN’s specific surface area, band gap, chemical composition, and structure, as well as the efficient separation of photogenerated charge carriers from the ground state (HOMO) to the excited state (LUMO), making it a top candidate for CO2 photoreduction. At the same time, this approach paves the path for the bottom-up fabrication of carbon nitride nanosheets.

Assessment of CO2 photoconversion over TiO2/La2O3 treated with acetic acid

TiO2/La2O3 treated with different concentration acetic acid was successfully synthesized via sol-gel method and fumigation. Compared with untreated TiO2/La2O3, acetic acid treated TiO2/La2O3 photocatalysts exhibited higher CO2 conversion efficiency. 0.7 mol L−1 acetic acid functionalized TiO2/La2O3 photocatalyst demonstrated highest CO2 conversion efficiency (97.6%). The mechanism was researched through different characterization methods including HRTEM, FTIR, Py-IR, XPS, et al. The increased performance over TiO2/La2O3 treated with acetic acid for CO2 photoconversion is mainly due to following three factors: (1) more hydroxyls on the surface of photocatalysts promote the adsorption of CO2, (2) the number of hole traps which can inhibit the recombination of photogenerated electrons and holes increases, (3) the formation of active oxygen vacancysites is promoted by La2O3 modified and the present of Lewis acidic sites.

CeO2/CuO/TiO2 heterojunction photocatalysts for conversion of CO2 to ethanol

An attempt to reduce CO2 emissions has led to the development of CeO2/CuO/TiO2 heterojunction photocatalysts for photoconversion of CO2 to useful products, e.g. ethanol. Composite photocatalysts were simply prepared by mixing TiO2 (P25) with different mass ratios of CeO2 (1 wt%) and CuO (2 or 3 wt%) by ball milling. The prepared photocatalysts had uniformly distributed CeO2 and CuO phases, throughout the TiO2 phase. The integration of CeO2 and CuO into TiO2 at 1 wt% CeO2 and 3 wt% CuO produced a composite, with a reduced band gap of 2.88 eV, allowing absorption of lower energy light and a lower electron–hole recombination rate. The 1%CeO2/3%CuO/TiO2 photocatalysts yielded ethanol at 30.5 μmol gcat −1 h−1, almost three times higher than the yield from pure TiO2. This improved CO2 conversion efficiency was due to contributions from properties of both additives: CeO2 increased light absorption, while CuO acted as an electron trap and enhanced CO2 adsorption. In addition, the heterojunction at the interfaces facilitated the photogenerated charge separation, which, in turn, increased the charge participation in the catalyzed conversion reactions.

Design and fabrication of photocatalytic coatings with α/β-Bi2O3 and recycled-fly ash for environmental remediation and solar fuel generation

To promote a circular economy, alkali-activated recycled fly ash (AAFA) can be used as an alternative binder for fabricating mortar coatings. The AAFA binder can also be functionalized with photocatalysts for application in environmental remediation. Here, α/β-Bi2O3 homojunction photocatalysts were incorporated into AAFA mortar coatings to confer photocatalytic properties for two applications, namely, self-cleaning and solar fuel generation from CO2 photoconversion. The α/β-Bi2O3 homojunctions were prepared using three methods. The homojunctions had a higher proportion of the β-Bi2O3 phase compared to α-Bi2O3; additionally, they exhibited with a 2D morphology and a bandgap suitable for visible-light activation. X-ray diffraction and energy dispersive spectroscopy analysis of the mortar coatings showed that the inorganic matrix comprised two frameworks based on calcium silicate hydrate and aluminosilicate hydrate, with high porosity. The photocatalytic mortar coatings exhibited self-cleaning activity, with the highest efficiency of 31%. This result was corroborated by total organic carbon analysis, which showed ~15% mineralization. The specimens also showed high activity for CO2 photoconversion to solar fuels such as formic acid (1932 μmol/g) and methanol (6 μmol/g) under visible light. These results were related to the synergistic effect of the mesoporous framework developed after alkaline activation, more efficient charge transfer in the homojunctions, enhanced CO2 affinity, and the presence of CaO, MgO, Na2O, and SiO2 in the binder. The efficiencies for both applications are comparable to those reported previously. The present approach is potentially applicable not only for minimizing the environmental impact of waste materials by reducing the disposal of fly ash in landfills, but also for producing value-added compounds and reducing the maintenance cost of buildings.