Search

We introduce a new graphene oxide (GO)-based membrane architecture that hosts cobalt catalysts within its nanoscale pore walls. Such an architecture would not be possible with catalysts in nanoscale, the current benchmark, since they would block the pores or alter the pore structure. Therefore, we developed a new synthesis procedure to load cobalt in an atomically dispersed fashion, the theoretical limit in material downsizing. The use of vitamin C as a mild reducing agent was critical to load Co as dispersed atoms (Co

Tailoring the coordination number (CN) of metal atoms has been increasingly recognized as one of the strategies to enhance the catalytic performance of single-atom catalysts (SACs). We here present...

Separating the redox sites of photocatalysts is one of most promising strategies to promote an efficient photoinduced charge transfer of semiconductor photocatalysis. Herein, we present a site-sele...

Nanotechnology has driven scientific advances in catalytic materials and processes over the past few decades. Unique physicochemical and electronic properties that emerge when materials are enginee...

Nanoscale catalysts that can enable Fenton-like chemistry and produce reactive radicals from hydrogen peroxide activation have been extensively studied in order to overcome the limitations of homogeneous Fenton processes. Despite several advantageous features, limitation in mass transfer of short-lived radical species is an inherent drawback of the heterogeneous system. Here, we present a mechanistic foundation for the way spatial confinement of Fenton chemistry at the nanoscale can significantly enhance the kinetics of radical-mediated oxidation reactions-pollutant degradation in particular. We synthesized a series of Fe3O4-functionalized nanoreactors with precise pore dimensions, based on an anodized aluminum oxide template, to enable quantitative analysis of nanoconfinement effects. Combined with computational simulation of spatial distribution of radicals, we found that hydroxyl radical concentration was strongly dependent on the distance from the surface of Fenton catalysts. This distance dependency significantly influences the gross reaction kinetics and accounts for the observed nanoconfinement effects. We further found that a length scale below 25 nm is critical to avoid the limitation of short-lived species diffusion and achieve kinetics that are orders of magnitude faster than those obtained in a batch suspension of heterogeneous catalysts. These findings suggest a new strategy to develop an innovative heterogeneous catalytic system with the most effective use of hydroxyl radicals in oxidation treatment scenarios.

We here present a novel Ti4O7-based electrode loaded with amorphous Pd clusters that achieve efficient anodic destruction of perfluorooctanoic acid (PFOA), a persistent water pollutant with significant environmental and human health concerns. These amorphous Pd clusters were characterized by the disordered, noncrystalline arrangement of Pd single atoms in close proximity, in contrast to crystalline Pd nanoparticles that have been often employed to tailor the electronic properties of an electrode. We found that the Ti4O7 electrode loaded with amorphous Pd clusters significantly outperformed the Ti4O7 electrode loaded with crystalline Pd particles due to enhanced electron transfer through dominant Pd-O bonds. Combined with the efficient binding of PFOA and its degradation intermediates to the fluorinated electrode surface, this electrode was capable of mineralizing PFOA and releasing fluoride as F-. The reaction pathway was found to proceed without involving reactive oxygen species and therefore was not quenched by common anions in complex natural water systems such as chloride ions.

Efforts to combine photocatalysts with organic and inorganic adsorbents in engineered composite materials have been pursued extensively to harness sunlight for a green, sustainable regeneration of exhausted adsorbent. Recent advances combining benchmark photocatalyst, titanium dioxide (TiO2), with an inorganic adsorbent, layered double hydroxides (LDHs), have shown potential for an inorganic adsorbent-photocatalyst system but faced critical limitations in realizing practical applications: low adsorption capacity and slow, inefficient photocatalytic regeneration. This study presents an enhanced TiO2/LDH based material that demonstrates a dramatically increased efficiency for both decontamination through adsorption and subsequent solar, photocatalytic regeneration. The combination of delamination and high temperature treatment of LDH is utilized to drastically enhance the adsorption capacity toward model contaminant Methyl Orange to 1450-1459 mg/g, which is even higher than most commercial and lab-synthesized carbon-based adsorbents. Light-active plasmonic nanoparticles are employed to increase the photocatalytic regeneration performance, and experimental results show that the synthesized composite material regains above 97% of its adsorption capacity for 5 cycles of regeneration and readsorption. Overall, the results of this study demonstrate potential for the development of inorganic multifunctional adsorbents that can harness a variety of chemical reactions without the loss of adsorptivity over long-term use.

Single atom catalysts have been found to exhibit superior selectivity over nanoparticulate catalysts for catalytic reactions such as hydrogenation due to their single-site nature. However, improved selectively is often accompanied by loss of activity and slow kinetics. Here we demonstrate that neighboring Pd single atom catalysts retain the high selectivity merit of sparsely isolated single atom catalysts, while the cooperative interactions between neighboring atoms greatly enhance the activity for hydrogenation of carbon-halogen bonds. Experimental results and computational calculations suggest that neighboring Pd atoms work in synergy to lower the energy of key meta-stable reactions steps, i.e., initial water desorption and final hydrogenated product desorption. The placement of neighboring Pd atoms also contribute to nearly exclusive hydrogenation of carbon-chlorine bond without altering any other bonds in organohalogens. The promising hydrogenation performance achieved by neighboring single atoms sheds light on a new approach for manipulating the activity and selectivity of single atom catalysts that are increasingly studied in multiple applications., Single atom catalysts have exhibited high selectivity for hydrogenation, yet improved selectively is often accompanied by loss of activity. Here the authors report that synergistic interactions of neighboring Pd single atoms lead to both high activity and selectivity for hydrodehalogenation catalysis.

Heterogeneous advanced oxidation processes (AOPs) allow for the destruction of aqueous organic pollutants via oxidation by hydroxyl radicals (•OH). However, practical treatment scenarios suffer from the low availability of short-lived •OH in aqueous bulk, due to both mass transfer limitations and quenching by water constituents, such as natural organic matter (NOM). Herein, we overcome these challenges by loading iron oxychloride catalysts within the pores of a ceramic ultrafiltration membrane, resulting in an internal heterogeneous Fenton reaction that can degrade organics in complex water matrices with pH up to 6.2. With •OH confined inside the nanopores (∼ 20 nm), this membrane reactor completely removed various organic pollutants with water fluxes of up to 100 L m-2 h-1 (equivalent to a retention time of 10 s). This membrane, with a pore size that excludes NOM (>300 kDa), selectively exposed smaller organics to •OH within the pores under confinement and showed excellent resiliency to representative water matrices (simulated surface water and sand filtration effluent samples). Moreover, the membrane exhibited sustained AOPs (>24 h) and could be regenerated for multiple cycles. Our results suggest the feasibility of exploiting ultrafiltration membrane-based AOP platforms for organic pollutant degradation in complex water scenarios.

Photocatalysis that utilizes semiconductor nanoparticles is one of the most investigated environmental nanotechnologies. It is a promising technology for air purification because it can decompose gaseous pollutants (particularly volatile organic compounds (VOCs)) directly into harmless CO2 and H2O under ambient conditions. Photocatalysis can be particularly suitable for removing low concentration pollutants (sub-ppm levels) in indoor environments where conventional adsorption technologies are not very efficient. Although photocatalytic air purification has been extensively investigated, it still falls far short of satisfying the requirements for practical usage. This review focuses on two main critical issues for improving the applicability of photocatalytic air purification: (1) increasing visible light activity to utilize ambient light and (2) preventing catalyst deactivation that hinders long-term usage of photocatalysts. Literature reports on the photocatalytic degradation of VOCs using visible light are surveyed and systematically categorized based on the type of photocatalytic materials and VOCs. Strategies taken to significantly increase the efficiency of visible light photocatalysts are introduced. On the other hand, photocatalyst deactivation processes are discussed according to the kinds of air pollutants, and various methods of assessing the extent of photocatalyst deactivation are outlined. The development of deactivation-resistant photocatalysts and their applications to air purification are also introduced and discussed. Finally, the status and the problems of the current research on photocatalytic air purification are critically discussed and suggestions for future studies of photocatalytic air purification are made.

Photocatalytic air purification is widely regarded as a promising technology, but it calls for more efficient photocatalytic materials and systems. Here we report a strategy to introduce an in-situ water (self-wetting) layer on WO3 by coating hygroscopic periodic acid (PA) to dramatically enhance the photocatalytic removal of hydrophilic volatile organic compounds (VOCs) in air. In ambient air, water vapor is condensed on WO3 to make a unique tri-phasic (air/water/WO3) system. The in-situ formed water layer selectively concentrates hydrophilic VOCs. PA plays the multiple roles as a water-layer inducer, a surface-complexing ligand enhancing visible light absorption, and a strong electron acceptor. Under visible light, the photogenerated electrons are rapidly scavenged by periodate to produce more •OH. PA/WO3 exhibits excellent photocatalytic activity for acetaldehyde degradation with an apparent quantum efficiency of 64.3% at 460 nm, which is the highest value ever reported. Other hydrophilic VOCs like formaldehyde that are readily dissolved into the in-situ water layer on WO3 are also rapidly degraded, whereas hydrophobic VOCs remain intact during photocatalysis due to the “water barrier effect”. PA/WO3 successfully demonstrated an excellent capacity for degrading hydrophilic VOCs selectively in wide-range concentrations (0.5−700 ppmv)., Photocatalytic air purification is promising but it calls for more efficient photocatalytic materials and systems. Here, the authors report a strategy to introduce an in-situ water layer on WO3 by coating hygroscopic periodic acid that effectively remove hydrophilic volatile organic compounds.

We here present a novel Ti

TiO2 nanotubes (TNT) have a highly ordered open structure that promotes the diffusion of dioxygen and substrates onto active sites and exhibit high durability against deactivation during the photocatalytic air purification. Herein, we synthesized {001} facet-exposed TiO2 nanotubes (001-TNT) using a new and simple method that can be easily scaled up, and tested them for the photocatalytic removal of volatile organic compounds (VOCs) in both a laboratory reactor and a commercial air cleaner. While the surface of TNT is mainly composed of {101} facet anatase, 001-TNT’s outer surface was preferentially aligned with {001} facet anatase. The photocatalytic degradation activity of toluene on 001-TNT was at least twice as high as that of TNT. While the TNT experienced a gradual deactivation during successive cycles of photocatalytic degradation of toluene, the 001-TNT did not exhibit any sign of catalyst deactivation under the same test conditions. Under visible light irradiation, the 001-TNT showed degradation a...

TiO2 nanoparticles modified with surface platinization or/and surface fluorination (Pt/TiO2, F-TiO2, and F-TiO2/Pt) were prepared to test their durability as an air-purifying photocatalyst. Toluene was selected as a target substrate for this test. Although Pt/TiO2 showed higher photocatalytic degradation activity than bare TiO2, Pt/TiO2 underwent rapid deactivation during repeated degradation cycles. F-TiO2 was deactivated to a lesser degree but its initial photocatalytic degradation activity was lower than bare TiO2. On the other hand, F-TiO2/Pt exhibited the highest photocatalytic activity and durability for toluene degradation. The surface fluorination that should replace the hydroxyl groups on TiO2 surface facilitates the formation of mobile OH radicals instead of surface-bound OH radicals. The surface platinization enhances the lifetime of charge carriers and makes more holes efficiently react with adsorbed water molecules. Through the remote photocatalytic oxidation of stearic acid and coumarin coated on a glass plate that was separated from the photocatalyst film with a small air gap (50 μm), it was observed that F-TiO2/Pt film generated the largest amount of mobile OH radicals that migrate through the air gap. The photocatalytic oxidation mediated by mobile OH radicals efficiently hindered the deposition of carbonaceous intermediates on the F-TiO2/Pt surface and increased the mineralization efficiency of VOCs, which consequently increased the durability of photocatalyst during VOC degradation.

Metal-organic frameworks (MOFs), built through the interconnection between metal clusters and di- to poly-topic organic linkers, have porous crystalline and tunable structures with many meritful properties such as robustness, high surface area/porosity, and adjustable pore size. As such, MOFs have drawn a great deal of attention in the design of the advanced heterogeneous catalytic materials. As the distribution of the catalytically active sites can be controlled further via post-synthesis modification (PSM), the use of Schiff base for such PSM is considered a promising strategy to develop highly active as well as stable catalysts. The great utility of Schiff base complex-anchored MOF is in fact recognized from various catalytic reactions (e.g., coupling, epoxidation, hydrogenation, and oxidation) through efficient coordination of metal ions. These catalysts are advantageous to overcome the common limitations of both homogeneous catalysis (e.g., poor recyclability as well as reusability) and heterogeneous catalysis (e.g., low activity). This review is hence expected to deliver actionable knowledge for the development of highly effective Schiff base/MOF catalysts via PSM for diverse catalytic applications.

Catalytic approaches are regarded as a highly favorable option to treat carcinogenic volatile organic compounds (VOCs: e.g., formaldehyde) released from various sources in indoor and outdoor environment. Among a wide range of engineered materials (e.g., metal oxide-supported noble metals), platinized titanium dioxide (Pt/TiO2) is recognized as a highly effective multi-functional catalyst (e.g., thermocatalyst, photocatalyst, and photothermal-catalyst (as a synergistic combination of the former two)). In this review, an in-depth discussion is offered to describe the applicability of this multi-functional platform towards the removal of gaseous pollutants in light of its numerous advantages (e.g., high removal efficiency, stability, regenerability, and sustainability). Further, the discussion is expanded to address the effects of diverse variables on its performance including inherent material characteristics (e.g., surface chemistry, structure, morphology, and functionalities), process variables (e.g., relative humidity, temperature, and reactant composition), and the underlying mechanisms. To this end, quantitative criteria are established to pursue an evaluation of its performance in a less biased manner for each of all different types of catalytic functions. Finally, the current knowledge gaps and suitable research avenues are discussed for an in-depth exploration of this unique catalytic system.

We synthesized freestanding doubly open-ended TiO2 nanotubes (DNT) film and compared their photocatalytic activity and durability during the repeated degradation cycles of volatile organic compounds (VOCs) with those of TiO2 nanotubes (TNT) film. DNT exhibited higher activity and durability for the photocatalytic degradation of gaseous acetaldehyde and toluene than TNT. The doubly open-ended structure of DNT allows O2 molecules to be easily supplied to the active sites, which increases not only the intrinsic photocatalytic activity but also the resistance to catalyst deactivation. The freestanding DNT film was additionally loaded with TiO2 nanoparticles (NP@DNT) in the inner wall to further increase the activity for VOC degradation. The photocatalytic activity of NP@DNT was higher than bare DNT and bare TNT by 1.3 and 1.8 times, respectively. Unlike the case of DNT, the TiO2 nanoparticles loaded TNT (NP@TNT) exhibited a lower activity than bare TNT, probably because the TiO2 nanoparticles blocked the TNT channels with hindering the mass transfer of O2 and VOC molecules. DNT with doubly open-ended structure serves as a versatile platform of fabricating nanostructured photocatalysts with maintaining the open channel structure that facilitates the mass transfer of O2 and VOC molecules.

Upconversion (UC) of sub-bandgap photons extends the effective light absorption range of photovoltaic and photocatalytic devices, allowing them to reach higher conversion efficiencies. Recent advances in polymer host materials make it possible to translate triplet-triplet annihilation (TTA)-UC, the UC mechanism most suitable for this purpose, to solid films that can be integrated into devices. The promise of these films is currently limited by the narrow light absorption of TTA-UC sensitizer chromophores, but incorporating multiple sensitizers into layered film systems presents a promising strategy for producing UC materials with broadened light absorption. This strategy is herein applied for photocatalytic air purification, demonstrating its use in a real-world application for the first time. We superimpose optimized red-to-blue and green-to-blue UC films within dual-layer systems and develop a new photocatalyst compatible with their fluorescence emission. By integrating the dual-layer UC film systems with films of this photocatalyst, we produce the first devices that use TTA-UC to harness both red and green sub-bandgap photons for hydroxyl radical generation and photocatalytic degradation of gaseous acetaldehyde, a model volatile organic compound (VOC). Under white light-emitting diode excitation, the dual-layer film systems' broadened light absorption enhances their devices' photocatalytic degradation efficiency, enabling them to degrade twice as much acetaldehyde as their single-sensitizer counterparts. We show that as a result of the different absorption profiles of the two sensitizers, the film order significantly impacts UC fluorescence and VOC degradation. By probing the influence of the excitation light source, excitation geometry, and chromophore spectral overlap on the film systems' UC performance, we propose a framework for the design of multilayer TTA-UC film systems suitable for integration with a variety of photovoltaic and photocatalytic devices.

Nanomaterials-based biomimetic catalysts with multiple functions are necessary to address challenges in artificial enzymes mimicking physiological processes. Here we report a metal-free nanozyme of modified graphitic carbon nitride and demonstrate its bifunctional enzyme-mimicking roles. With oxidase mimicking, hydrogen peroxide is generated from the coupled photocatalysis of glucose oxidation and dioxygen reduction under visible-light irradiation with a near 100% apparent quantum efficiency. Then, the in situ generated hydrogen peroxide serves for the subsequent peroxidase-mimicking reaction that oxidises a chromogenic substrate on the same catalysts in dark to complete the bifunctional oxidase-peroxidase for biomimetic detection of glucose. The bifunctional cascade catalysis is successfully demonstrated in microfluidics for the real-time colorimetric detection of glucose with a low detection limit of 0.8 μM within 30 s. The artificial nanozymes with physiological functions provide the feasible strategies for mimicking the natural enzymes and realizing the biomedical diagnostics with a smart and miniature device., Glucose oxidase (GOx) and horseradish peroxidase (HRP) are used as an enzymatic cascade for blood glucose monitoring. Here, the authors developed a metal-free, graphitic carbon nitride-based nanozyme with GOx- and HRP-like activities and combine it with a microfluidic reactor for real-time glucose monitoring.

Among the diverse wastewater treatment routes, photoelectrocatalysis (PEC) developed by hybridization of photocatalyst with electrocatalyst has been demonstrated for a high potential in waste-to-energy applications. Here, we provide a comprehensive review to assess the technical readiness level of PEC techniques for both wastewater treatment and energy recovery, with a particular emphasis on the pulp and paper (P&P) industry. The effects of various experminetal parameters (e.g., electrode materials, reactor types, and experimental conditions) on the removal of organic pollutants from P&P effluents with the simultaneous recovery of energy (e.g., H2 and H2O2) have been evaluated in relation to the PEC performance metrics (e.g., quantum yield (QY), space–time yield (STY), and figure of merit (FoM) metrics). Critical challenges in the augmentation of PEC are also summarized in terms of cost analysis, energy consumption, and durability. At last, future research prospects of the PEC system under the real-world conditions are discussed.

The engineering of oxygen vacancies in CeO2 nanoparticles (NPs) allows the specific fine-tuning of their oxidation power, and this can be used to rationally control their activity and selectivity in the photocatalytic oxidation (PCO) of aromatic pollutants. In the current study, a facile strategy for generating exceptionally stable oxygen vacancies in CeO2 NPs through simple acid (CeO2-A) or base (CeO2-B) treatment was developed. The selective (or mild) PCO activities of CeO2-A and CeO2-B in the degradation of a variety of aromatic substrates in water were successfully demonstrated. CeO2-B has more oxygen vacancies and exhibits superior photocatalytic performance compared to CeO2-A. Control of oxygen vacancies in CeO2 facilitates the adsorption and reduction of dissolved O2 due to their high oxygen-storage ability. The oxygen vacancies in CeO2-B as active sites for oxygen-mediated reactions act as (i) adsorption and reduction reaction sites for dissolved O2, and (ii) photogenerated electron scavenging sites that promote the formation of H2O2 by multi-electron transfer. The oxygen vacancies in CeO2-B are particularly stable and can be used repeatedly over 30 h without losing activity. The selective PCOs of organic substrates were studied systematically, revealing that the operating mechanisms for UV-illuminated CeO2-B are very different from those for conventional TiO2 photocatalysts. Thus, the present study provides new insights into the design of defect-engineered metal oxides for the development of novel photocatalysts.

Proper co-catalysts (usually noble metals), combined with semiconductor materials, are commonly needed to maximize the efficiency of photocatalysis. Search for cost-effective and practical alternatives for noble-metal co-catalysts is under intense investigation. In this work, nanodiamond (ND), which is a carbon nanomaterial with a unique sp3(core)/sp2(shell) structure, was combined with WO3 (as an alternative co-catalyst for Pt) and applied for the degradation of volatile organic compounds under visible light. NDs-loaded WO3 showed a highly enhanced photocatalytic activity for the degradation of acetaldehyde (∼17 times higher than bare WO3), which is more efficient than other well-known co-catalysts (Ag, Pd, Au, and CuO) loaded onto WO3 and comparable to Pt-loaded WO3. Various surface modifications of ND and photoelectochemical measurements revealed that the graphitic carbon shell (sp2) on the diamond core (sp3) plays a crucial role in charge separation and the subsequent interfacial charge transfer. As a...

This study introduces graphited nanodiamond (G-ND) as an environmentally friendly, easy-to-regenerate, and cost-effective alternative catalyst to activate persulfate (i.e., peroxymonosulfate (PMS) and peroxydisulfate (PDS)) and oxidize organic compounds in water. The G-ND was found to be superior for persulfate activation to other benchmark carbon materials such as graphite, graphene, fullerene, and carbon nanotubes. The G-ND/persulfate showed selective reactivity toward phenolic compounds and some pharmaceuticals, and the degradation kinetics were not inhibited by the presence of oxidant scavengers and natural organic matter. These results indicate that radical intermediates such as sulfate radical anion and hydroxyl radical are not majorly responsible for this persulfate-driven oxidation of organic compounds. The findings from linear sweep voltammetry, thermogravimetric analysis, Fourier transform infrared spectroscopy, and electron paramagnetic resonance spectroscopy analyses suggest that the both pers...

We designed a scaffold-like porous titanium nitride (TiN) nanotube (NT) as a catalyst support for Pt to facilitate the oxygen reduction reaction. Bulk titanium nitride, which is known as an electrically conductive material, is compatible with other metals. As the size of TiN particles decreases, however, they lose their intrinsic high electrical conductivity, due to a series of nanoparticle grain boundaries acting as electron reservoirs and traps. A designed grain-boundary-free scaffold-like porous TiN NT which is analogous to the shape of the one-dimensional porous human spine exhibits high electrical conductivity in spite of having a surface area similar to that of TiN nanoparticle (NPs). The electrical conductivity of TiN NTs is ca. 30-fold higher than that of spherical TiN NPs. The electrochemical oxygen reduction measurements between porous TiN NT and TiN NPs after Pt loading clearly exhibit the superiority of TiN NT as a catalyst support. The results from various electrochemical measurements suggest...

We synthesized ordered TiO2 nanotubes (TNT) and compared their photocatalytic activity with that of TiO2 nanoparticles (TNP) film during the repeated cycles of photocatalytic degradation of gaseous toluene and acetaldehyde to test the durability of TNT as an air-purifying photocatalyst. The photocatalytic activity of TNT showed only moderate reduction after the five cycles of toluene degradation, whereas TNP underwent rapid deactivation as the photocatalysis cycles were repeated. Dynamic SIMS analysis showed that carbonaceous deposits were formed on the surface of TNP during the photocatalytic degradation of toluene, which implies that the photocatalyst deactivation should be ascribed to the accumulation of recalcitrant degradation intermediates (carbonaceous residues). In more oxidizing atmosphere (100% O2 under which less carbonaceous residues should form), the photocatalytic activity of TNP still decreased with repeating cycles of toluene degradation, whereas TNT showed no sign of deactivation. Because TNT has a highly ordered open channel structure, O2 molecules can be more easily supplied to the active sites with less mass transfer limitation, which subsequently hinders the accumulation of carbonaceous residues on TNT surface. Contrary to the case of toluene degradation, both TNT and TNP did not exhibit any significant deactivation during the photocatalytic degradation of acetaldehyde, because the generation of recalcitrant intermediates from acetaldehyde degradation is insignificant. The structural characteristics of TNT is highly advantageous in preventing the catalyst deactivation during the photocatalytic degradation of aromatic compounds.

Volatile organic compounds (VOCs) having the same number of carbon atoms with different functional groups were selected to investigate the substrate-specific mineralization and deactivation behaviors of TiO2. The mineralization rate of VOCs decreased in the order of n-propylaldehyde > n-propanol >> n-propylamine > n-propanethiol > n-chloropropane, which indicates that the presence of heteroatoms significantly retards the mineralization rate. The mineralization of tested VOCs is closely related to the efficient production of aldehydes as intermediates. During the PCD, the formation of carbonaceous deposits on the TiO2 surface was observed, which was the most significant with n-propylamine, much less with other VOCs, and negligible with n-chloropropane. The repeated PCD cycles of n-propylamine and n-propanethiol caused the significant deactivation of TiO2, while those of other VOCs little reduced their PCD activity. The photocatalyst deactivation is associated with the deposition of non-volatile products on the TiO2 surface such as carbonaceous residues, ammoniums, and sulfates.

TiO

This study demonstrates the first reported photocatalytic decomposition of an indoor air pollutant, acetaldehyde, using low-energy, sub-bandgap photons harnessed through sensitized triplet–triplet annihilation (TTA) upconversion (UC). To utilize low-intensity noncoherent indoor light and maximize photocatalytic activity, we designed a plasmon-enhanced sub-bandgap photocatalyst device consisting of two main components: (1) TTA-UC rubbery polymer films containing broad-band plasmonic particles (Ag-SiO2) to upconvert sub-bandgap photons, and (2) nanodiamond (ND)-loaded WO3 as a visible-light photocatalyst composite. Effective decomposition of acetaldehyde was achieved using ND/WO3 (Eg = 2.8 eV) coupled with TTA-UC polymer films that emit blue photons (λEm = 425 nm, 2.92 eV) upconverted from green photons (λEx = 532 nm, 2.33 eV), which are wasted in most environmental photocatalysis. The overall photocatalytic efficiency was amplified by the broad-band surface plasmon resonance of AgNP-SiO2 particles incorpor...