HCHO Removal Efficiency Research Articles

Tuning the nitrogen contents in carbon matrix encapsulating Co nanoparticles for promoting formaldehyde removal through Mott-Schottky effect

The increment of N dopants in carbon matrix can effectively enrich the electron density of N-doped carbon encapsulating metal nanoparticles (NPs) via Mott-Schottky effect, thereby favoring the activation of molecular O2 with abundant free electrons on carbon surface. Herein, given the essential role of oxygen activation in formaldehyde (HCHO) oxidation, Co NPs-embedded nitrogen-doped carbon and carbon nanotubes (Co/NCNT) with controllable N contents (2.30 ~ 4.38 wt%) were prepared and utilized for catalytic oxidation of HCHO at room temperature. Electron transfer from the Co core to the N-doped carbon layer was modulated by the tailorable concentrations of N dopant through the Mott-Schottky effect at their interface, being validated by X-ray and ultraviolet photoelectron spectroscopy, as well as CO2 temperature-programmed desorption experiment. The catalytic activity increased gradually with the elevation of nitrogen content, achieving a HCHO removal efficiency of approximately 80% over Co/NCNT-5 with the maximum nitrogen content. Combined with the comprehensive characterizations, the mechanism underlying the catalytic activity improvement in HCHO oxidation induced by the Mott-Schottky effect was proposed. This work provides a new insight into optimizing the non-noble metal catalysts for HCHO oxidation at room temperature.

Degradation of Formaldehyde over MnO2/CeO2 Hollow Spheres: Elucidating the Influence of Carbon Sphere Self-Sacrificing Templates.

Here, we prepare a MnO2/CeO2 hollow sphere catalyst using the carbon sphere as a self-sacrificing template for formaldehyde (HCHO) removal. In the feed gas of 20 ppm of HCHO (balanced by N2) + 20 vol % O2, a HCHO removal efficiency of 70% was achieved at 20 °C and full conversion was reached at around 47 °C at GHSV = 50,000 mL (gcat h)−1 for MnO2/CeO2 hollow spheres. The catalytic performance and structural and chemical properties of MnO2/CeO2 hollow spheres for the removal of core carbon spheres were explored, and the influence of using the carbon sphere as a self-sacrificing template was proved by comparing with carbon@MnO2/CeO2 (a core carbon sphere with a MnO2/CeO2 shell) and nonmorphologic MnO2/CeO2. The properties of the MnO2/CeO2 hollow spheres are significantly improved compared to carbon@MnO2/CeO2 (removal efficiency of 45% at 150 °C) and MnO2/CeO2 (removal efficiency of 46% at 20 °C) as a result of an evolution in the interaction between Mn/Ce and carbon. This increase in the interaction strength seems to (i) increase the oxygen vacancy, (ii) promote the oxygen species mobility, and (iii) improve the chemical stability of the MnO2/CeO2 hollow spheres. We believe that these results are beneficial to the fabrication of binary transition metal oxides and applications of them in HCHO removal.

Surface modification of cellulose nanocrystals via SI-AGET ATRP and application in waterborne coating for removing of formaldehyde

The hazardous indoor air pollutants of formaldehyde (HCHO) are harmful for human health. Nowadays, it is important to design and fabricate green and efficient HCHO removal materials for HCHO removal from polluted indoor air. In this manuscript, cellulose nanocrystals (CNCs) as green nanomaterials were successfully surface-initiated by 2-(methacryloyloxy)ethyl acetoacetate (MEAA) as functional monomer via surface-initiated Activator Generated by Electron Transfer Atom Transfer Radical Polymerization (SI-AGET ATRP) for the application in removal of HCHO. The employment of CNCs/Poly(2-(methacryloyloxy)ethyl acetoacetate) (CNCs@PMEAA) as nanocomposites were further implanted self-healing waterborne coating for an effective way to remove HCHO. From the result, the HCHO removal efficiency reached 97.5% of CNCs@PMEAA-type coating within 300 min at room temperature, which was much higher than that of the conventional coating (82.8%). This study provides some promising green methods for designing nanocomposite's waterborne coating to remove HCHO at room temperature.

Indoor light boosted formaldehyde abatement over electrostatic self-assembled graphitic carbon nitride/ceric oxide at ambient temperature

The pursuit of efficient noble metal-free catalysts is highly desirable for possible practical application of ambient-temperature removal of indoor formaldehyde (HCHO). In this work, graphitic carbon nitride/ceric oxide (g-C3N4/CeO2) heterojunctions were prepared via a simple electrostatic self-assembly method, which possessed moderate catalytic performances for HCHO elimination in the dark at ambient temperature. Indoor fluorescent-light irradiation obviously sped up the conversion of HCHO into CO2 and H2O over g-C3N4/CeO2 heterojunctions. Particularly, C3N4/CeO2 with theoretical 20 wt% of g-C3N4 (20%g-C3N4/CeO2) exhibited a HCHO removal efficiency of ca. 73% and HCHO conversion ratio of ca. 70% under fluorescent-lamp illumination, higher than the corresponding ones of 47% and 26% in the dark, respectively. The fluorescent-lamp irradiation promoting HCHO degradation over C3N4/CeO2 was proposed on the basis of the visible-light response of individual g-C3N4 and CeO2, and the distinct heterostructure conducive to the separation of photo-generated carriers as well as intrinsic capability of CeO2 favoring the formation of extra active oxygen species. This work might provide a vane of energy saving and emission reduction by taking full advantage of indoor lights for environmental remediation.

Immobilization of Silver Doped Titanium Dioxide onto Stainless Steel Wire Mesh for Photocatalytic Degradation of Gaseous Formaldehyde under Visible Light Irradiation

Titanium dioxide (TiO2) photocatalysis can degrade air pollutants into nontoxic substances but it can only be excited by UV light. To eliminate this limitation, silver (Ag) and/or graphene oxide (GO) doped TiO2 are applied to enhance visible light photocatalytic activity. In this study, Ag-TiO2 (0.5%, 1%, 2% w/w), GO/TiO2 and GO/Ag-TiO2 were synthesized and then coated on stainless steel mesh. Crystalline and molecule structures, chemical compositions and optical properties of the prepared photocatalyst samples were characterized with X-ray diffraction spectroscopy, X-ray fluorescence spectroscopy, Raman spectroscopy, UV-visible diffuse reflectance spectroscopy, Fourier-transform infrared spectroscopy, and Scanning electron microscopy equipped with Energy dispersive X-ray spectroscopy techniques. The photocatalytic performances of the various doped catalysts were evaluated according to their abilities to degrade gaseous formaldehyde (HCHO) under visible light. The effect of operational parameters on the photocatalytic degradation of HCHO including layer numbers of photocatalyst, powers of fluorescent lamp and flow rates of HCHO were observed. The results indicated that the presence of Ti, O and Ag elements in Ag-TiO2 and Ti, O, Ag and C elements in GO/Ag-TiO2 was confirmed. Proper dispersion of the photocatalyst on the wire mesh was exhibited. Under visible light, the incorporation of Ag and GO in TiO2 photocatalysts produced higher degradation rates of HCHO than pure TiO2. The optimum operating conditions of HCHO degradation at initial concentration of 108.71.15 ppm over visible light irradiation for 30 min were 5 layers of 0.5% Ag-TiO2, 72 W fluorescent light and 300 ml/min of HCHO flow rate. Under these conditions, the removal efficiency of gaseous HCHO was 76.70±0.73%.

Evaluation of foamed nickel photocatalytic filters for an air cleaner on removal of formaldehyde in the indoor environment

Foamed nickel photocatalytic filters based on zinc oxide and fitted to standard air cleaner are assessed under the same indoor air quality conditions in a real test site setting with UV light applied via a suitable lamp. Environmental parameters determined using a chamber test are input to the mass balance model and airflow analysis software (CONTAM) to simulate the change of HCHO concentration with time at the real test site. The mass balance model is validated by mean absolute percentage error (MAPE). Results of the environmental control chamber test for ZnO filters at 60 min interval show the highest removal efficiency for HCHO are under no UV light irradiation. It also shows that regardless of whether the UV lamp is on or off, the highest removal efficiency for HCHO is under high humidity and low concentration. The removal efficiency of HCHO with application of UV light is not significantly affected by low humidity and low concentration. Clean air delivery rates (CADR) of the air cleaner are consistent with HCHO removal efficiency, i.e., higher CADR brings higher removal efficiency. The results show the removal efficiency of HCHO by TiO2 photocatalytic filters is higher than that obtained with ZnO photocatalytic filters under UV light irradiation. For the real test site, the MAPEs of the simulations are 13.52 ~ 38.80% for changes of HCHO concentrations in 20 min interval with mass balance model and CONTAM. The MAPEs of HCHO for CONTAM simulations is 5.38%, which shows the CONTAM has good.

Hydroxylation and sodium intercalation on g-C3N4 for photocatalytic removal of gaseous formaldehyde

In this study, hydroxyl-modified/Na-intercalated g-C3N4 was used as an effective material for the removal of gaseous formaldehyde (HCHO) through adsorption and photocatalytic oxidation. In a simple reflux reaction using different NaOH concentrations, the surface-grafted hydroxyl (‒OH) groups of g-C3N4 formed internal hydrogen bonds with gaseous HCHO, while the Na atoms intercalated into the layered structure of g-C3N4 to create an electron transfer path (layer‒Na‒layer) to improve charge separation for photocatalytic oxidation. The hydroxylation as well as Na intercalation of g-C3N4 significantly increased its HCHO removal efficiency compared with that of bare g-C3N4. The HCHO removal capacity of the modified g-C3N4 reached approximately 0.12 ppm g−1 min−1, which was twice that of bare g-C3N4 (<0.06 ppm g−1 min−1). Moreover, the modified g-C3N4 was reused at least thrice without any decline in activity. This work provides a facile, simple, and fast approach to the modification of g-C3N4 via hydroxylation and Na intercalation to enhance HCHO adsorption as well as electron transfer, rendering it a promising material for indoor HCHO removal.

Complete catalytic oxidation of formaldehyde at room temperature on MnxCo3-xO4 catalysts derived from metal-organic frameworks

Developing cost-effective non-noble catalysts for completely decomposing formaldehyde (HCHO) into harmless CO2 and H2O at room temperature remains great challenges for indoor air purification. Herein, MnxCo3-xO4 solid solutions are prepared via the calcination of metal-organic frameworks (MOFs) with different Co/Mn molar ratios. The catalyst (Mn1Co1) achieves 100 % HCHO removal at room temperature for the first time, and possesses excellent stability. During an intermittent test and a non-stop 34 -h test, the HCHO removal efficiency remains almost 100 %. The complete oxidation of HCHO is confirmed by the disappearance of HCHO peaks and the increase of CO2 peak intensity in effluent gas analysis. In situ DRIFTS results show that formate species is the main intermediate and it can be further oxidized to CO2 and H2O as final products in the presence of water vapor. The superior catalytic activity and stability of the Mn1Co1 catalyst endow its great potential in the HCHO removal application.

Highly efficient simultaneous removal of HCHO and elemental mercury over Mn-Co oxides promoted Zr-AC samples

MnxCoy/Zrz-AC prepared by impregnation method was investigated on the simultaneous removal of HCHO and Hg0. The samples were characterized by BET, SEM, XRD, H2 pulse chemisorption, H2-TPR, XPS, Hg-TPD and in-situ DRIFTS. Thereinto, the optimal Mn2/3Co8/Zr10-AC achieved 99.87% HCHO removal efficiency and 82.41% Hg0 removal efficiency at 240 °C, respectively. With increased surface area and pore volume, Zr-AC support facilitated higher dispersion of MnOx-CoOx. Moreover, the co-doping of MnOx-CoOx endowed the sample with more active oxygen species and higher reducibility, which further facilitated the removal of HCHO and Hg0. Chemisorption was proved to predominate in Hg0 removal, and oxidation also worked as Hg2+ was detected in outlet gas. Besides, HCHO predominated in the competition of active oxygen species, especially for lattice oxygen, thus suppressed the Hg0 removal. According to in-situ DRIFTS, HCHO removal proceeded as HCHOads → DOM → formate species → CO2 + H2O, and was boosted by active oxygen species. Furthermore, Mn2/3Co8/Zr10-AC was proved with excellent regeneration performance, indicating its potential in practical application.

Removal of formaldehyde by triboelectric charges enhanced MnOx-PI at room temperature

Indoor formaldehyde (HCHO) pollution has become a serious issue to threaten human health. Therefore, it is urgent to develop long-term and efficient HCHO removal materials and technology with low energy consumption. In this study, the MnOx was deposited in-situ by hydrothermal synthesis on the hydrolyzed PI fibers. By harvesting the kinetic energy of wind, triboelectric charges and electric field are generated between MnOx-PI and nylon fibers. The employment of triboelectric charges on the catalyst is an effective way to increase conversion rates of O*, which may help to accelerate the decomposition of intermediates, enhance efficiency, and enlarge the life of the catalyst. As a result, during the static testing, the HCHO removal efficiency reached 92.4% of MnOx-PI-1.0 h-nylon within 1100 mins at room temperature, which was much higher than that of the MnOx-PI-1.0 h sample (56.3%). In addition, the removal efficiency of the MnOx-PI-2.0 h-nylon remained above 95% during the 48-hours dynamic test. The present study provides a new route to achieve long-term efficient removal of HCHO in the indoor environment and extended the application for the nano-triboelectric in the catalytic field.

CoMn2O4 supported on carbon nanotubes for effective low-temperature HCHO removal

Formaldehyde (HCHO) is harmful to environment and human health, even at extremely low concentrations. Catalytic oxidation on metal oxides is an effective method for HCHO removal. Transition metal oxides have attracted much attention due to its advantages of low cost and good redox properties, but it requires the high reaction temperature and energy consumption to reach the good catalytic activity for HCHO removal. In this work, Mn-Co mixed oxides supported on carbon nanotubes (CNTs) were prepared for enhancing the low-temperature catalytic activity of HCHO removal. The results of XRD, TEM and XPS characterization confirmed the formation of CoMn2O4 solid solution on CNTs. The highest relative content of Co3+, Mn3+ and active lattice oxygen were achieved at the optimal composition of 3Mn-1Co. The HCHO oxidation test showed that CoMn2O4/CNTs (3Mn-1Co) had the best catalytic activity at 160 °C, obtaining 95% HCHO (100 ppm) removal efficiency and 95% CO2 selectivity at GHSV = 30,000 mL gcat-1 h-1. Compared with the similar catalysts previously reported in literatures, CoMn2O4/CNTs was of the lower T90 value for HCHO oxidation.

Self-assembled NaY/MnO2-based textiles for indoor formaldehyde removal at room temperature

Through a simple self-assembly method, the as-synthesized NaY/MnO2 nanocomposites were uniformly distributed and immobilized on textile fibers, which make the nanocomposite suit for indoor formaldehyde (HCHO) removal. Compared with NaY-based textiles and MnO2-based textiles, the NaY/MnO2-based textiles using polyester (PET) as substrate exhibited superior HCHO removal activity and better stability at room temperature. Furthermore, for low-level indoor environment, HCHO removal efficiency of NaY/MnO2-based textiles was up to 90 % even after 30 cycles tests under the conditions of original HCHO concentration of 1 ppm. Therefore, the NaY/MnO2-based textiles highlighted new avenues to the practical use for low-level indoor HCHO removal.

Novel Materials for Combined Nitrogen Dioxide and Formaldehyde Pollution Control under Ambient Conditions

Formaldehyde (HCHO) and nitrogen dioxide (NO2) often co-exist in urban environments at levels that are hazardous to health. There is a demand for a solution to the problem of their combined removal. In this paper, we investigate catalysts, adsorbents and composites for their removal efficiency (RE) toward HCHO and NO2, in the context of creating a pollution control device (PCD). Proton-transfer-reaction mass spectrometry and cavity ring-down spectrometry are used to measure HCHO, and chemiluminescence and absorbance-based monitors for NO2. Commercially available and lab-synthesized materials are tested under relevant conditions. None of the commercial adsorbents are effective for HCHO removal, whereas two metal oxide-based catalysts are highly effective, with REs of 81 ± 4% and 82 ± 1%, an improvement on previous materials tested under similar conditions. The best performing material for combined removal is a novel composite consisting of a noble metal catalyst supported on a metal oxide, combined with a treated active carbon adsorbent. The composite is theorized to work synergistically to physisorb and oxidize HCHO and chemisorb NO2. It has an HCHO RE of 72 ± 2% and an NO2 RE of 96 ± 2%. This material has potential as the active component in PCDs used to reduce personal pollution exposure.

Pt Anchored on Mn(Co)CO3/MnCo2O4 Heterostructure for Complete Oxidation of Formaldehyde at Room Temperature

AbstractMn(Co)CO3/MnCo2O4 hybrids were prepared via a hydrothermal following by heat‐treatment process and used as novel supports of Pt nanoparticles for formaldehyde (HCHO) removal at room temperature. The catalyst heat‐treated at 150 °C had a primary nanorod‐like morphology, however, its well‐defined structure was obviously collapsed when the heat‐treatment temperature was above 350 °C. In the static experiment where indoor HCHO removal was simulated at room temperature, the catalyst heat‐treated at 150 °C with only 0.4 wt % Pt showed the best catalytic activity among the investigated samples, which possessed a HCHO removal efficiency of 92.2 % in 60 min under the initial HCHO concentration at approximately 180 ppm. The unique nanorod feature and heterogeneous interface between MnCo2O4 and Mn(Co)CO3 (MnCO3 and CoCO3) with a proper weight ratio are the main contributions to the superior catalytic performance of the catalyst by boosting the charge transfer and active oxygen species formation in the process of HCHO catalytic oxidation reaction. Our work indicates that well‐defined morphological heterostructures which facilitate the charge migration and formation of reactive oxygen species, could be the potential alternative catalysts in the enhancement of HCHO decomposition at room temperature.

Defective domain control of TiO2 support in Pt/TiO2 for room temperature formaldehyde (HCHO) remediation

Sustainable and effective formaldehyde (HCHO) remediation at room temperature has significant potential in next-generation indoor environment purification technology. Herein, defective anatase TiO2 was synthesized using chemical vapor condensation (CVC) and was subsequently impregnated with 0.08 wt% Pt. The resulting Pt/CVC-TiO2 catalyst was used for the room-temperature conversion of HCHO and exhibited a HCHO removal efficiency of 80% under continuous flow conditions (GHSV 100,000 cm3 h−1 gcat−1) with an initial concentration of 10 ppm with good stability over 600 min. The characterization results confirmed the metallic oxidation state (Pt0), oxygen vacancies (mainly F centers), disordered domains, and strong interaction between Pt and defective TiO2 were essential for high activity. Moreover, electron paramagnetic resonance (EPR) analysis showed the consistent stability of the defective domains of CVC-TiO2, imparting catalytic stability over multiple cycles. This study highlights the synergistic relationship between oxygen vacancies in the TiO2 support and the resulting HCHO oxidation functionality.

Oxygen vacancy–engineered δ-MnOx/activated carbon for room-temperature catalytic oxidation of formaldehyde

Although oxygen vacancies (OVs) commonly act as adsorption/active sites in catalytic oxidation of formaldehyde (HCHO), thereby strongly influencing catalyst activity, their control and translation into scale-up products for practical application remain challenging. Herein, δ-MnOx/activated carbon was synthesized via in situ reduction coupled with ammonia modification, and the developed method was found to allow easy OV control for large-scale production. OV concentration was effectively regulated through adjustment of Mn3+ content, and OV roles in the catalytic reaction were probed by several techniques. The optimized catalyst featured superior HCHO removal efficiency and CO2 selectivity at room temperature, mainly due to oxygen activation by abundant OVs to form reactive oxygen species. The intermediates and pathways of HCHO removal were investigated. Thus, this work provides insights into the enhancement of active site exposure through OV control for a single bulk catalyst and demonstrates its applicability for efficient and commercially viable room-temperature oxidation of HCHO.

Enhancing the room-temperature catalytic degradation of formaldehyde through constructing surface lewis pairs on carbon-based catalyst

In this study, we construct the surface Lewis pairs, involving electron-rich nitrogen (Lewis base) sites and electron-deficient carbon (Lewis acid) sites, on carbon-based catalysts to enhance the catalytic activity towards the room-temperature decomposition of formaldehyde (HCHO). Density functional theory (DFT) calculation results show that the Lewis pairs, especially pyrrolic nitrogen species, contributed to the efficient HCHO adsorption ability. After the adsorbed HCHO molecules are oxidized into CO2 and H2O, and the Lewis acid-base catalytic sites finally get re-exposed, further initiating the next round of HCHO adsorption-decomposition process. Experimental measurements found that the typical sample exhibits an excellent catalytic HCHO oxidation activity, with the maximum HCHO removal efficiency of about 98.0 %, and the catalytic activity remains relatively unchanged after five cycles of reuse. This study may also open a new strategy to construct novel Lewis pairs for the removal of HCHO from other heteroatom-doped (e.g., B, S, F) porous carbon-based materials.

Manganese dioxide-filled hierarchical porous nanofiber membrane for indoor air cleaning at room temperature

Indoor air pollution, including atmospheric particular matter 2.5 (PM2.5) and chemical gaseous pollutants (HCHO), has been an ongoing concern. Seeking a practical strategy for protection of the indoor air quality (IAQ) remains a challenge. Herein, we demonstrated a hierarchical porous membrane consisting of the birnessite-type MnO2 that was filled in the polystyrene porous nanofibers (MnO2/PS HPNM) fabricated by a versatile electrospinning method. The effective air cleaning of both PM2.5 and HCHO at remarkably low resistance was achieved by dominating the hierarchical porous structure. The HCHO gas could easily permeate through the mesopores of the PS nanofibers and contact MnO2, thereby resulting in an excellent HCHO removal efficiency of 88.2% after the initial run and 74% after five cycles. In addition, the pore-filling MnO2 with the layered structure increased the nanofiber membrane surface area, thus enhancing its PM capture performance (99.77%). Moreover, the macropores from the interwoven nanofibers ensured clean air penetration leading to a low airflow resistance of 82 Pa. The hierarchical multifunction porous structure membrane provided a new approach for the IAQ protection.

Synthesis of MnO2 modified porous carbon spheres by preoxidation-assisted impregnation for catalytic oxidation of indoor formaldehyde

Resin-based porous carbon spheres with well dispersed MnO2 particles were sucessfully synthesised by steam activation and preoxidation-assisted impregnation of manganese nitrate salt. X-ray diffractometer (XRD), Fourier Transform Infrared spectroscopy (FT-IR), N2 adsorption–desorption, scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), H2 temperature programmed reduction (H2-TPR), O2 temperature-programmed desorption (O2-TPD) and in-situ diffuse reflectance fourier transform spectrometry (DRIFTS) were applied to characterize the obtained porous carbon spheres, and the HCHO adsorption and stability performances were evaluated in a fixed bed reactor. The results demonstrated that surface chemical properties and HCHO removal performances were significantly enhanced after the modification of preoxidation-assisted impregnation. The optimal manganese nitrate loading value, and relative humidity were 6 and 50%, respectively. Moreover, the higher HCHO concentration showed a smaller breakthrough time. The HCHO removal efficiency of ACS–O-6% Mn remained 100% even after reaction for 20 h at room temperature, while the average HCHO removal efficiency only declines by 0.2% compared with the first adsorption after 10 regeneration cycles. The in-situ DRIFTS results showed the smaller accumulation and faster desorption of intermediate products over the ACS–O-6% Mn. The HCHO removal mechanism analysis indicated that the enriched Mn3+ and surface active chemisorbed oxygen accounted for the excellent catalytic oxidation activity and stability.

Hierarchical Ni/Co-LDHs catalyst for catalytic oxidation of indoor formaldehyde at ambient temperature

Catalytic oxidation of formaldehyde (HCHO) at ambient temperature is an effective method for indoor HCHO removal. In this study, Ni/Co-Layered double hydroxides (LDHs) with different molar ratios were successfully synthesized via a one-step hydrothermal method. Their structure and morphology were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET)-specific surface area, X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR), respectively. The catalytic activity results show that Ni/Co-LDHs with the Ni/Co ratio of 1:2 exhibited enhanced activity for HCHO decomposition. The removal efficiency of indoor HCHO was up to 99.7% at ambient temperature, and it remained highly stable without any obvious deactivation even after a reaction time of 800 min. The abundant hydroxyl groups were favorable for catalytic activity, which could not only enrich the adsorption of HCHO on the surface of catalysts, but also directly react with HCHO to obtain CO2 and H2O. Moreover, the redox cycles of Ni3+/Ni2+ and Co3+/Co2+ would provide more reactive oxygen species and therefore promote catalytic reaction. This work can provide a new insight into LDH-based catalysts for low-concentration HCHO removal in practical application.