HCHO Adsorption Research Articles

The interaction between HCHO and TiO2 (1 0 1) surface without and with water and oxygen molecules

The interactions between formaldehyde (HCHO) molecule and TiO2 (1 0 1) surface without and with water and oxygen were studied using density functional theory calculations. The adsorption energy of HCHO adsorption on TiO2 surface without water and oxygen is −360.96 kJ/mol, and HCHO molecule is not dissociated. The oxygen and carbon atoms of HCHO are bonded to the titanium and oxygen (O1) atoms of TiO2 surface, respectively, and form a dioxymethylene (CH2O2) structure. The adsorption energy of HCHO adsorption on TiO2 surface system with water and oxygen is −723.40 kJ/mol, and O2, H2O and HCHO molecules are all dissociated. HCHO molecule not only interacts with TiO2 surface, but also combines with O2 molecule. Two CH bonds of HCHO are broken, one hydrogen atom (H1) is bonded to the oxygen atom (O2) of O2, while another hydrogen atom (H2) is bonded to the O atom (O1) of TiO2 surface. The remaining CO bond that the dissociated and new formed HO bonds can be oxidized to form carbon dioxide and water in subsequent action by oxygen from the atmosphere. H2O and O2 molecules have a great effect on the degradation process of HCHO molecule on TiO2 (1 0 1) surface.

Synergetic effect of Cu and Mn oxides supported on palygorskite for the catalytic oxidation of formaldehyde: Dispersion, microstructure, and catalytic performance

In this study, palygorskite (Pal), a natural nanorod-like clay mineral, is applied as the support of mixed Cu Mn oxides for formaldehyde (HCHO) oxidation, with focus on their dispersion, microstructure, and relative role during the catalytic oxidation. The composite material loaded with Cu Mn oxides retains the nanorod-like morphology of Pal, while the oxide particles in the size of 10–40 nm are well dispersed in the slit pores stacked by rods of Pal. Most of the Cu Mn oxides on Pal are with spinel structure, where Cu2+ ions occupy the tetrahedral sites and Mn3+ ions occupy the octahedral sites. The Pal-supported Cu Mn oxides achieves 90% CO2 generation at 207-258 °C, and displays better catalytic performance than solely supported catalyst. The presence of Cu obviously improves the reducibility of composite and the adsorption of HCHO, resulting in the acceleration of HCHO oxidation. The water resistance of composite catalyst also enhances with the increase of Cu content. Based on all these benefits, the catalytic performance of Cu Mn oxides on Pal can be optimized with an increase of Cu level.

HCHO oxidation over highly dispersed Au nanoparticles supported on mesoporous silica with superior activity and stability

We firstly reported highly active Au nanoparticles catalyst supported on mesoporous silica for low-temperature HCHO oxidation. Amine as the positively charged groups was post grafted onto the surface of mesoporous silica before gold loading (PG), and it showed 15% HCHO conversion to CO2 at room temperature and complete conversion was obtained at 55 °C. No activity decrease was observed within 8 h. As comparison, mesoporous silica supported Au catalysts was also prepared by straightforward chemical reduction (CR) and impregnation (IM), which behaved poor HCHO catalytic activity with complete conversions at 200 °C and 90 °C respectively. The activation energy (Ea) for HCHO oxidation over PG was 17.6 kJ/mol, which was much lower than those (22.2–50.2 kJ/mol) over IM and CR samples. It was found that amine-functionalized mesoporous silica contributed to the well-dispersed and uniform Au nanoparticles with the optimal size distribution about 2–4 nm, and large amounts of low-coordinated Au atoms and electronic structure like bulk Au were observed on these Au nanoparticles, which accelerated HCHO adsorption and transformation into intermediate species like DOM, formate and CO(a). Particularly, the interaction between amine and Au effectively inhibited the reduction of Auδ+ to Au0, which positively contributed to the best catalytic performance. Moreover, Au/SiO2 system prepared by amine post-grafting method showed poor activity of complete combustion at 210 °C. Comparatively, it was proposed that MCM-41 with well-ordered and open ends of pore structure showed better HCHO adsorption-diffusion capacity and the ability of controlling Au particles in high dispersion, which was great benefit to the high catalytic activity of HCHO oxidation.

Promotional removal of HCHO from simulated flue gas over Mn-Fe oxides modified activated coke

A series of MnxFey/AC catalysts synthesized by impregnation method were investigated on the efficient and stable removal of HCHO in the fix-bed reactor. Extensive characterizations, BET, SEM, XRD, H2-TPR, XPS and FT-IR, were conducted to study the physicochemical properties, HCHO oxidation and surface reaction of catalysts. The optimal Mn0.75Fe6.02/AC showed enhanced HCHO removal efficiency of 98.30%, as well as excellent performance for simultaneous removal of HCHO (89.96%) and Hg0 (77.51%). NO and SO2 balanced in N2 would inhibit the removal of HCHO, while the addition of 6% O2 weakened the negative effect of SO2 and NO + 6% O2 facilitated the removal of HCHO. Besides, the slight promotion effect of water vapor was contributed to the regeneration of consumed −OH via the activation of surface oxygen by adsorbed H2O. Characterization results indicated that Mn0.75Fe6.02/AC possessed larger BET surface area, well-developed porosity and better dispersion of active components. Mn0.75Fe6.02/AC exhibited higher reducibility due to the synergistic effect between MnOx and FeOx, and the interaction between Mn-Fe oxides and AC support. At the same time, the oxygen-containing functional groups (C-O-, COO), abundant active surface oxygen and –OH facilitated both adsorption and oxidation of HCHO. Besides, the formate and carbonate intermediates formed on the surface of Mn0.75Fe6.02/AC in HCHO removal process, which could be further oxidized into CO2 and H2O. On the basis of above investigations, the mechanism of enhanced HCHO catalytic removal over MnxFey/AC was proposed.

Solid strong base K-Pt/NaY zeolite nano-catalytic system for completed elimination of formaldehyde at room temperature

Solid strong base nano-catalytic system of K-modification NaY zeolite supported 0.08% Pt (K-Pt/NaY) were constructed for eliminating HCHO at room temperature. In the catalytic process, activation energy over K-Pt/NaY nano-catalytic system was greatly decreased along with the enhanced reaction rate. Characterization and catalytic tests revealed the surface electron structure of K-Pt/NaY was improved, as reflected by the enhanced HCHO adsorption capability, high OH concentration, and low-temperature reducibility. Therefore, the optimal K-Pt/NaY showed high catalytic efficiency and strong H2O tolerance for HCHO elimination by directly promoting the reaction between active OH and formate species. These results may suggest a new way for probing the advanced solid strong base nano-catalytic system for the catalytic elimination of indoor HCHO.

Ultrathin Bi2WO6 nanosheet decorated with Pt nanoparticles for efficient formaldehyde removal at room temperature

Two-dimensional (2D) ultrathin bismuth tungstate (Bi2WO6) nanosheets (BWO-NS) with a thickness of approximately 4.0 nm were synthesized by a one-step hydrothermal method, and decorated with platinum (Pt) nanoparticles (NPs) via an impregnation/borohydride-reduction approach. The as-prepared ultrathin Pt-BWO-NS exhibited superior catalytic activity for removing gaseous formaldehyde (HCHO) at ambient temperature, in comparison with bulk counterpart with Bi2WO6 sheet thickness of tens of nanometers. The ultrathin structure endowed the Pt-BWO-NS sample with larger specific surface area, which can provide abundant surface active sites for HCHO adsorption and facilitate the homogeneous dispersion of Pt NPs. X-ray photoelectron spectroscopy and hydrogen temperature-programmed reduction analyses revealed the interaction between the Bi2WO6 support and Pt species, which is crucial for activating surface oxygen atoms to participate in the catalytic HCHO oxidation process. By conducting in situ diffuse reflectance infrared Fourier transform spectroscopy under different atmospheres, i.e., gaseous HCHO in nitrogen or oxygen (O2), the reaction mechanism and the role of O2 were elucidated, with dioxymethylene, formate and linearly adsorbed carbon monoxide identified as the main reaction intermediates. This study may provide new enlightenment on fabricating novel 2D nanomaterials for efficient indoor air purification and potentially other environmental applications.

Synchronous pore structure and surface hydroxyl groups amelioration as an efficient route for promoting HCHO oxidation over Pt/ZSM-5

Catalytic removal of trace HCHO at room temperature over supported noble metal catalysts has been an interesting topic. For practical application, both the intrinsic activity of the catalyst and mass transfer should be taken into consideration due to the low indoor HCHO concentration. Herein, we provide a facile way for simultaneously enhancing HCHO adsorption, storage and oxidation over Pt/ZSM-5 by aqueous NaOH treatment, as well as synchronous pore structure and surface hydroxyl groups amelioration. With proper amount of NaOH modification, Pt/ZSM-5 shows a high HCHO conversion above 99% and a (>) 1000 h good stability at 30 °C, a space velocity of 30000 mL h−1 g−1 and initial 50 ppm HCHO with a low 0.2 wt.% Pt loading amount, which is among the best of state-of-the-art novel metal catalysts. These results show that the consideration of both morphology manipulation and surface hydroxyl groups tailoring is important in designing an efficient HCHO oxidation catalyst.

Strong base g-C3N4 with perfect structure for photocatalytically eliminating formaldehyde under visible-light irradiation

Solid strong base systems of g-C3N4 by inducing potassium (KC3N4) were constructed for photocatalytically decomposing HCHO. Characterization and theoretical calculation revealed that the formation of K-C and K-N perfected the π-conjugated structure of g-C3N4, which greatly enhanced the basicity, improve optical and electrical properties of g-C3N4. In the photocatalytic process, K-improved π-conjugated structure promoted HCHO adsorption, activation, completely oxidative decomposition under visible-light irradiation. Therefore, KC3N4 photocatalysts presented high efficiency in photocatalytic elimination of HCHO, and the optimal apparent rate reached 0.21 mol−0.17 L0.17 min−1 with 1.17 reaction order by promoting the reaction between active oxygen (OH and OH) and formate species under visible-light irradiation, which was 30 times of that (0.007 mol−0.17 L0.17 min−1) over pristine g-C3N4. These results may suggest a new way for probing the advanced solid strong base photocatalysts for eliminating volatile organic compounds.

Adsorption of gaseous air pollutants over Ti-doped ZGNR structures: a DFT study

In this study, we employed the density functional theory (DFT) to study the interactions between gaseous air pollutants, including di-atomic (CO and NO), tri-atomic (CO2 and HCN), and poly-atomic (HCHO and COCl2) species, and Ti-doped zigzag graphene nanoribbon (ZGNR) structures. During this, two types of doped structures are considered, i.e., SV-ZGNR in which Ti replaces one carbon atom and DV-ZGNR, in which Ti atom replaces two adjacent carbon atoms. All gases under consideration are observed to exhibit significant adsorption energy over doped ZGNR except COCl2 for which a catalytic dissociation is observed. Our results indicate that doped ZGNR is better for CO, NO, and HCHO adsorption as compared to that for reported doped graphene sheet. Also, DV-ZGNR is preferred over SV-ZGNR in terms of adsorption. Moreover, due to the adsorption, changes in the density of states are observed which confirms that the Ti-doped ZGNR has potential to be used as the sensing platform for these gases.

Adsorption of gaseous air pollutants over Ti-doped ZGNR structures: a DFT study

In this study, we employed the density functional theory (DFT) to study the interactions between gaseous air pollutants, including di-atomic (CO and NO), tri-atomic (CO2 and HCN), and poly-atomic (HCHO and COCl2) species, and Ti-doped zigzag graphene nanoribbon (ZGNR) structures. During this, two types of doped structures are considered, i.e., SV-ZGNR in which Ti replaces one carbon atom and DV-ZGNR, in which Ti atom replaces two adjacent carbon atoms. All gases under consideration are observed to exhibit significant adsorption energy over doped ZGNR except COCl2 for which a catalytic dissociation is observed. Our results indicate that doped ZGNR is better for CO, NO, and HCHO adsorption as compared to that for reported doped graphene sheet. Also, DV-ZGNR is preferred over SV-ZGNR in terms of adsorption. Moreover, due to the adsorption, changes in the density of states are observed which confirms that the Ti-doped ZGNR has potential to be used as the sensing platform for these gases.

Ab initio characterization and experimental validation on the roles of oxygen-containing groups in graphene based formaldehyde sensors.

The development of formaldehyde (HCHO) sensors employing reduced graphene oxide (rGO) as sensing materials calls for a profound, atomic level understanding on the roles of oxygen-containing groups. In this work, the performances of rGO-based HCHO sensors were investigated using ab initio calculations and experimental validation. Density functional theory (DFT) simulations were performed to calculate the adsorption energy (Eads) and charge transfer (ΔQ) for the adsorption of HCHO on pristine graphene, rGO with epoxides, rGO with hydroxyl groups, and rGO with carboxyl groups. The results show that the incorporation of oxygen-containing groups leads to an obvious increase of Eads and ΔQ values, with an order of carboxyl group > hydroxyl group > epoxides > pristine graphene. The increase of Eads and ΔQ values could increase the variation in the concentration of charge carriers, the change of conductance of the sensing materials, and hence the sensor response. The experimental measurements indicate that with a decrease in the C/O atomic ratio from 16.2 to 6.6, the sensor response to 1 ppm HCHO increases from 0.10% to 0.73%, confirming the DFT calculation results. Moreover, even with a certain C/O atomic ratio of ∼6.6, rGO with 6.80% carboxyl groups exhibits a distinctly larger response to 0.2-3 ppm HCHO, compared with the counterpart with 3.09% carboxyl groups. The as-obtained insights into the effects of oxygen-containing groups on the response of rGO to HCHO could be instructive for preparing rGO-based HCHO sensors for advanced performances.

A theoretical study of formaldehyde adsorption and decomposition on a WC (0001) surface.

A lot of research attention has been paid to designing and exploring efficient adsorbents for HCHO adsorption and decomposition. Herein, we have demonstrated a highly active material, WC, for HCHO adsorption through first-principles calculations. Due to the exposed three-coordinated W atoms (W3c) of the WC (0001) surface, HCHO molecules can be settled on the WC (0001) surface through newly formed OF–W3c and/or CF–W3c bonds, forming different adsorption configurations. When settled on the WC (0001) surface, the molecular configuration of the HCHO molecule and the corresponding CF–HF and CF–OF bond lengths would be greatly changed. Due to the enlarged CF–HF and CF–OF bond lengths, the adsorbed HCHO molecules tend to dissociate through two possible pathways; these are the two-step CF–HF bond scission or the one-step CF–OF bond scission. The former results in two H adatoms and a CO molecule chemisorbed to the surface and the latter produces an O adatom and a CH2 group on the surface. Further Cl-NEB calculations demonstrate that the pre-adsorbed O atom has little influence on the first CF–HF bond scission and the CF–OF bond scission, while promoting the second CF–HF bond scission. Considering the dissociative products, H and CH2 have the potential to couple into a CH3 group (or even a CH4 molecule) and two CH2 groups may couple into a C2H4 molecule. In the end, we propose that OH ions may couple with the dissociative products of HCHO, so an alkali solution could be used to post-process the WC (0001) surface to restore its surface active sites. These results demonstrated the potential of WC in HCHO sensing and abatement.

Density Functional Theory Study of the Formaldehyde Catalytic Oxidation Mechanism on a Au-Doped CeO2(111) Surface

Formaldehyde is a harmful and toxic substance. Au-CeO2 catalysts show the excellent formaldehyde catalytic oxidation activity even under ambient temperatures. Here, we present the DFT+U calculations to investigate HCHO oxidation mechanisms and the effects of Au doping and multiple oxygen vacancies. The reaction process of HCHO oxidation mainly consists of the following steps: HCHO adsorption, C–H bond cleavages, CO2 desorption, O2 adsorption, and H2O formation and desorption. The doped Au reduces the energy barriers in C–H bond cleavages on the AuCe1–xO2(111) surface compared with the CeO2(111) surface. Au also leads to the activation of the surface oxygen species and then promotes HCHO adsorption and decreases the formation energies of oxygen vacancies. For HCHO adsorption and oxidation reaction on defective surfaces, catalysts with more oxygen vacancies possess higher adsorption energy and lower activation energy. These results provide deep insights into the effects of Au and multiple oxygen vacancies o...

CO and HCHO adsorption on FeO monowire devices: a DFT study

FeO monowire structures were constructed and optimized using density functional theory (DFT) to study the adsorption behavior of CO and HCHO gas phase molecules. The adsorption behavior of the target molecules was studied in terms of adsorption energy, charge density and the reaction time of the FeO monowire devices. Also, FeO monowire molecular devices are constructed to study the sensitivity of the devices towards CO and HCHO molecules using non-equilibrium Green’s function (NEGF) with density functional theory. The zero bias electronic transport properties confirm the adsorption of the CO and HCHO on the FeO monowire devices. From the V–I characteristic and the differential conductance calculations, the FeO monowire device is more sensitive to HCHO than CO molecule. However, the CO-adsorbed FeO monowire device exhibits high order of NDR behavior and can be used as a functional group for fabricating data storage device based FeO monowire.

A novel process of ozone catalytic oxidation for low concentration formaldehyde removal

AbstractTo reduce energy costs, minimize secondary pollution from undecomposed ozone, and improve the efficiency of ozone use, a novel process of cycled storage-ozone catalytic oxidation (OZCO) was employed to remove formaldehyde (HCHO) at low concentrations in air. We applied Al2O3-supported manganese oxide (MnOx) catalysts to this process, and examined the HCHO adsorption capacity and OZCO performance over the MnOx catalysts. Owing to the high dispersion of MnOx and low oxidation state of manganese, the MnOx/Al2O3 catalysts with a manganese acetate precursor and 10%-Mn loading showed good performance in both storage and OZCO stages. The presence of H2O led to a decrease of the HCHO adsorption capacity owing to competitive adsorption between moisture and HCHO at the storage stage; however, high relative humidity (RH) favored complete conversion of stored HCHO to CO2 at the OZCO stage and contributed to an excellent carbon balance. Four low concentration HCHO storage-OZCO cycles with a long HCHO storage period and relatively short OZCO period were successfully performed over the selected MnOx/Al2O3 catalyst at room temperature and a RH of 50%, demonstrating that the proposed storage-OZCO process is an economical, reliable, and promising technique for indoor air purification.

Highly active Pt/NaxTiO2 catalyst for low temperature formaldehyde decomposition

A series of titania nanowires containing different Na content (NaxTiO2) were prepared from sodium titanate by varying the pH value of ion-exchange. They were used to load the Pt nanoparticles for low temperature formaldehyde catalytic oxidation. As prepared samples were systematically characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS), temperature programmed reduction/desorption/oxidation (TPR/TPD/TPO) and so on. The results showed that NaxTiO2 were consisted of anatase and sodium titanate. As pH value increased, the surface area and anatase content of catalyst decreased. Pt particles on NaxTiO2 were more easily oxidized and had smaller size but less exposed atoms compared with those on pure TiO2. The HCHO catalytic oxidation result exhibited that Pt/NaxTiO2 catalysts possessed excellent HCHO catalytic oxidation at ambient temperature that were 8.9–52.8 times the activities as that of Pt/TiO2. Kinetic studies manifested the easy activation of HCHO reaction over Pt/NaxTiO2 catalysts. Structure-performance analysis showed that the enhanced performance of Pt/NaxTiO2 catalysts was mainly attributed to two factors: increase in HCHO adsorption amount and change in HCHO decomposition pathway. According to HCHO-DRIFTS, linearly adsorbed CO generated from formate can react with hydroxyls to be carbonate/bicarbonate over Pt/NaxTiO2 catalysts. Simultaneously, the formate in Pt/NaxTiO2 catalyst with high Na content was also decomposed into a weak adsorbed CO. Both reaction pathways avoided the strong adsorption of CO on Pt/NaxTiO2 catalysts, which can facilitate the HCHO decomposition.

Flexible room-temperature formaldehyde sensors based on rGO film and rGo/MoS2 hybrid film

Gas sensors based on reduced graphene oxide (rGO) films and rGO/MoS2 hybrid films were fabricated on polyethylene naphthalate substrates by a simple self-assembly method, which yielded flexible devices for detection of formaldehyde (HCHO) at room temperature. The sensing test results indicated that the rGO and rGO/MoS2 sensors were highly sensitive and fully recoverable to a ppm-level of HCHO. The bending and fatigue test results revealed that the sensors were also mechanically robust, durable and effective for long-term use. The rGO/MoS2 sensors showed higher sensitivities than rGO sensors, which was attributed to the enhanced HCHO adsorption and electron transfer mediated by MoS2. Furthermore, two kinds of MoS2 nanosheets were prepared by either hydrothermal synthesis or chemical exfoliation and were compared for their detection of HCHO, which revealed that the hydrothermally produced MoS2 nanosheets with rich defects led to enhanced sensitivity of the rGO/MoS2 sensors. Moreover, these fabricated flexible sensors can be applied for the HCHO detection in food packaging.

Synergetic effect of oxygen vacancy and Pd site on the interaction between Pd/Anatase TiO2(101) and formaldehyde: A density functional theory study

Insights into the functions and the synergetic effects of oxygen vacancy and noble metal sites on the performance of the reducible oxide supported noble metal catalysts are very important in designing formaldehyde catalysts. Herein, the roles of oxygen vacancies and Pd sites, and their synergistic effect on the interaction between HCHO and Pd/Anatase TiO2(101) surface were systematically studied by a density functional theory (DFT) study. It is found that both the presence of oxygen vacancy and Pd site can promote the HCHO adsorption over TiO2(101) surface. The presence of Pd site is beneficial for the oxygen vacancy formation by reducing its formation energy. Furthermore, synergetic effect of oxygen vacancy and Pd site on the interaction between Pd/TiO2(101) and HCHO is demonstrated for the case with the co-presence of oxygen vacancy and Pd site. In this situation, the oxygen atom of HCHO molecular occupies the oxygen vacancy and the carbon atom of HCHO connects with the Pd site, and a larger adsorption energy is obtained in comparison with the cases with only oxygen vacancy or Pd site present. These results indicate that both oxygen vacancy manufacturing and Pd doping can strength the HCHO adsorption over TiO2(101) surface, and their synergistic effects further promote the interaction between HCHO and Pd/TiO2 catalyst, which is beneficial for the HCHO oxidation.

Honeycomb-like micro-mesoporous structure TiO2/sepiolite composite for combined chemisorption and photocatalytic elimination of formaldehyde

Structured hybrid materials based on the combination adsorbent-photocatalyst have large surface area, an average pore diameter, good dispersion and strong adsorptivity, showing promising performance for environmental applications. In this study, honeycomb-like micro-mesoporous structure TiO2/sepiolite composites were fabricated using TiCl4 and modified sepiolite (MS) nanofibers as the precursors by a hydrolysis-precipitation method. The effect of the textural, morphological and structural properties of TiO2/sepiolite composites on the adsorption and photocatalytic degradation of formaldehyde (HCHO) in gas phase was analyzed. The results indicate that thermal treatment at 550 °C and TiO2/MS weight ratios of 1/2 ensure an optimum combination of textural, optical and HCHO adsorption and photocatalytic properties. At ambient temperature, the optimal catalyst (relative humidity of 45%, and HCHO initial concentration of 6.56 mg/m3) could efficiently decompose HCHO into CO2 and H2O, and still showed a good performance even after 4 cycles under UV irradiation. The excellent performance of the TiO2/sepiolite is primarily ascribed to the synergistic effect between the adsorbability of sepiolite nanofibers and the catalytic ability of TiO2 nanoparticles.

High-efficient physical adsorption and detection of formaldehyde using Sc- and Ti-decorated graphdiyne

In sensitive analysis, the ultimate limit is to achieve reliable detection on trace amount of molecules. In this work, Sc- and Ti-decorated graphdiyne were proposed as promising materials for high-efficient molecular detection. Using density functional theory calculations, we investigated the electronic response of single Sc- and Ti-atom-decorated graphdiyne to HCHO (as a typical air pollutant). Thermodynamic analysis predicted that Sc or Ti adatom could be stabilized on the corner sites of single-layer graphdiyne sheet, with migration barriers high enough to prevent Sc or Ti adatom aggregation. The adsorption of HCHO on Sc- or Ti-decorated graphdiyne was found stronger than on pristine graphene or graphdiyne, which provides a prerequisite for molecular sensing. The electronegativity of HCHO leads to strong electronic attraction from Sc or Ti adatom to HCHO, resulting in a remarkable decrease of carrier density in graphdiyne. On Ti-decorated graphdiyne, the electronic attraction of HCHO appears to be stronger than on Sc-decorated graphdiyne and changes the system from metal to n-doped semiconductor. Quantum transport calculations show a decrease of current caused by the adsorbed HCHO. The results systematically exhibit the electronic response of Sc- or Ti-decorated graphdiyne to HCHO and suggest them as promising materials for molecule detection.