CO Species Research Articles

Selective Increase in CO2 Electroreduction to Ethanol Activity at Nanograin‐Boundary‐Rich Mixed Cu(I)/Cu(0) Sites via Enriching Co‐Adsorbed CO and Hydroxyl Species

AbstractSelective producing ethanol from CO2 electroreduction is highly demanded, yet the competing ethylene generation route is commonly more thermodynamically preferred. Herein, we reported an efficient CO2‐to‐ethanol conversion (53.5 % faradaic efficiency at −0.75 V versus reversible hydrogen electrode (vs. RHE)) over an oxide‐derived nanocubic catalyst featured with abundant “embossment‐like” structured grain‐boundaries. The catalyst also attains a 23.2 % energy efficiency to ethanol within a flow cell reactor. In situ spectroscopy and electrochemical analysis identified that these dualphase Cu(I) and Cu(0) sites stabilized by grain‐boundaries are very robust over the operating potential window, which maintains a high concentration of co‐adsorbed *CO and hydroxyl (*OH) species. Theoretical calculations revealed that the presence of *OHad not only promote the easier dimerization of *CO to form *OCCO (ΔG~0.20 eV) at low overpotentials but also preferentially favor the key *CHCOH intermediate hydrogenation to *CHCHOH (ethanol pathway) while suppressing its dehydration to *CCH (ethylene pathway), which is believed to determine the remarkable ethanol selectivity. Such imperative intermediates associated with the bifurcation pathway were directly distinguished by isotope labelling in situ infrared spectroscopy. Our work promotes the understanding of bifurcating mechanism of CO2ER‐to‐hydrocarbons more deeply, providing a feasible strategy for the design of efficient ethanol‐targeted catalysts.

Study of CO2 Adsorption Properties on the SrTiO3(001) Surface with Ambient Pressure XPS.

The adsorption properties of CO2 on the SrTiO3(001) surface were investigated using ambient pressure X-ray photoelectron spectroscopy under elevated pressure and temperature conditions. On the Nb-doped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption, i.e., the formation of CO3 surface species, occurs first at the oxygen lattice site under 10-6 mbar CO2 at room temperature. The interaction of CO2 molecules with oxygen vacancies begins when the CO2 pressure increases to 0.25 mbar. The adsorbed CO3 species on the Nb-doped SrTiO3 surface increases continuously as the pressure increases but starts to leave the surface as the surface temperature increases, which occurs at approximately 373 K on the defect-free surface. On the undoped TiO2-enriched (1 × 1) SrTiO3 surface, CO2 adsorption also occurs first at the lattice oxygen sites. Both the doped and undoped SrTiO3 surfaces exhibit an enhancement of the CO3 species with the presence of oxygen vacancies, thus indicating the important role of oxygen vacancies in CO2 dissociation. When OH species are removed from the undoped SrTiO3 surface, the CO3 species begin to form under 10-6 mbar at 573 K, thus indicating the critical role of OH in preventing CO2 adsorption. The observed CO2 adsorption properties of the various SrTiO3 surfaces provide valuable information for designing SrTiO3-based CO2 catalysts.

Strong Electronic Interaction Enables Enhanced Solar-Driven CO2 Reduction into Selective CH4 on SrTiO3 with Photodeposited Pt2+ Sites.

Targeting selective CO2 photoreduction into CH4 remains a challenge due to the sluggish reaction kinetics and poor hydrogenation ability of the unstable intermediate. Here, the active Pt2+ sites were photodeposited on the SrTiO3 photocatalyst, which was well demonstrated to manipulate the CH4 product selectivity. The results showed that SrTiO3 mainly yielded the CO (6.98 μmol g-1) product with poor CH4 (0.17 μmol g-1). With the Pt2+ modification, 100% CH4 selectivity could be obtained with an optimized yield rate of 8.07 μmol g-1. The prominent enhancement resulted from the following roles: (1) the strong electronic interaction between the Pt2+ cocatalyst and SrTiO3 could prompt efficient separation of the photoelectron-hole pairs. (2) The Pt2+ sites were active to capture and activate inert CO2 into HCO3- and CO32- species and allowed fast *COOH formation with the lowered reaction barrier. (3) Compared with SrTiO3, the formed *CO species could be captured tightly on the Pt2+ cocatalyst surface for generating the *CH2 intermediate by the following electron-proton coupling reaction, thus leading to the CH4 product with 100% selectivity.

Synergy of Photogenerated Electrons and Holes toward Efficient Photocatalytic Urea Synthesis from CO2 and N2

AbstractDirectly coupling N2 and CO2 to synthesize urea by photocatalysis paves a sustainable route for urea synthesis, but its performance is limited by the competition of photogenerated electrons between N2 and CO2, as well as the underutilized photogenerated holes. Herein, we report an efficient urea synthesis process involving photogenerated electrons and holes in respectively converting CO2 and N2 over a redox heterojunction consisting of WO3 and Ni single‐atom‐decorated CdS (Ni1‐CdS/WO3). For the photocatalytic urea synthesis from N2 and CO2 in pure water, Ni1‐CdS/WO3 attained a urea yield rate of 78 μM h−1 and an apparent quantum yield of 0.15 % at 385 nm, which ranked among the best photocatalytic urea synthesis performance reported. Mechanistic studies reveal that the N2 was converted into NO species by ⋅OH radicals generated from photogenerated holes over the WO3 component, meanwhile, the CO2 was transformed into *CO species over the Ni site by photogenerated electrons. The generated NO and *CO species were further coupled to form *OCNO intermediate, then gradually transformed into urea. This work emphasizes the importance of reasonably utilizing photogenerated holes in photocatalytic reduction reactions.

Synergy of Photogenerated Electrons and Holes toward Efficient Photocatalytic Urea Synthesis from CO2 and N2.

Directly coupling N2 and CO2 to synthesize urea by photocatalysis paves a sustainable route for urea synthesis, but its performance is limited by the competition of photogenerated electrons between N2 and CO2, as well as the underutilized photogenerated holes. Herein, we report an efficient urea synthesis process involving photogenerated electrons and holes in respectively converting CO2 and N2 over a redox heterojunction consisting of WO3 and Ni single-atom-decorated CdS (Ni1-CdS/WO3). For the photocatalytic urea synthesis from N2 and CO2 in pure water, Ni1-CdS/WO3 attained a urea yield rate of 78 μM h-1 and an apparent quantum yield of 0.15 % at 385 nm, which ranked among the best photocatalytic urea synthesis performance reported. Mechanistic studies reveal that the N2 was converted into NO species by ⋅OH radicals generated from photogenerated holes over the WO3 component, meanwhile, the CO2 was transformed into *CO species over the Ni site by photogenerated electrons. The generated NO and *CO species were further coupled to form *OCNO intermediate, then gradually transformed into urea. This work emphasizes the importance of reasonably utilizing photogenerated holes in photocatalytic reduction reactions.

Rationally Designed L12-Pt2RhFe Intermetallic Catalyst with High CO-Tolerance for Alkaline Methanol Electrooxidation.

It is a grand challenge to deep understanding of and precise control over functional sites for the rational design of highly efficient catalysts for methanol electrooxidation. Here, an L12-Pt2RhFe intermetallic catalyst with integrated functional components is demonstrated, which exhibits exceptional CO tolerance. The Pt2RhFe/C achieves a superior mass activity of 6.43 A mgPt -1, which is 2.23-fold and 3.53-fold higher than those of PtRu/C and Pt/C. Impressively, the Pt2RhFe/C exhibits a significant enhancement in durability owing to its high CO-tolerance and stability. Density functional theory calculations reveal that high performance of Pt2RhFe intermetallic catalyst arises from the synergistic effect: the strong OH binding energy (OHBE) at Fe sites induce stably adsorbed OH species and thus facilitate the dehydrogenation step of methanol via rapid hydrogen transfer, while moderate OHBE at Rh sites promote the formation of the transition state (Pt-CO···OH-Rh) with a low activation barrier for CO removal. This work provides new insights into the role of OH binding strength in the removal of CO species, which is beneficial for the rational design of highly efficient catalysts.

Propane dehydrogenation performance of titanosilicate-1 supported CoOx catalysts by adjusting the acidity and reducibility

The development of low-cost and toxicity-free cobalt oxide-based catalysts for propane dehydrogenation to propylene (PDH) has gained momentum. In this paper, titanosilicate-1 (TS-1) supported CoOx catalysts doped with different alkali and alkaline earth metal ions (M = Na, K, Mg, Ca and Ba) were prepared by adjusting the acidity, reducibility and oxidation state to increase the activity and stability during the PDH reaction. It was found that the decrease in the number of Lewis acid sites and lack of Co2+Ox species with the addition of K ions led to an almost complete loss of the activity of the Co-K catalyst. However, Co-Ca catalyst exhibited moderate acidity, more Lewis acid sites, a larger amount of the in-situ formed highly-dispersed metallic Co0 nanoparticles (∼5 nm) and Co2+Ox species strongly interacting with the support, all of which were responsible for its highest space-time yield (STY) of propylene formation (0.88 kg h−1 kgcat.−1). Though Co3O4 particles were more active for the side reactions, they could be readily reduced to metallic Co0 nanoparticles during the PDH process, and increased the selectivity to propylene with time on stream. Specifically, it was demonstrated that the highly-dispersed metallic Co0 nanoparticles were also active for the PDH activity, but was lower than Co2+Ox species that were strongly interacted with TS-1 support. The deposited coke on the catalysts was related to the catalyst deactivation. The Co0 species could not completely return to the oxidation states after burning off the deposited coke, which seemed to be related to the incomplete recovery of catalytic activity after regeneration.

PdSnW Ternary Alloy Nanoparticle with Excellent CO Anti‐Poisoning Activity for Boosting Alkaline Ethanol Oxidation Reaction

AbstractEfficient ethanol oxidation reaction (EOR) catalysts with anti‐poisoning ability and high selectivity are in high demand for the widespread application of direct ethanol fuel cells (DEFCs). Here, the PdSnW ternary alloy nanoparticles are synthesized by a facile solvothermal method and exhibit an enhanced EOR catalytic performance. CO stripping experiment, X‐ray photoelectron spectroscopy and in situ Fourier transform infrared are employed to study the correlation between catalyst structure and EOR catalytic performance. The oxyphilic Sn and W not only provide dangling O−H bond, accelerating the subsequent oxidation of adsorbed intermediate CO species, but also moderate the electron state of Pd, enhancing the adsorption of CH3CH2OH, thus resulting in the promotion of C−C bond cleavage and an increased C1 selectivity. As a consequence, PdSnW alloy nanoparticle catalyst exhibit a better stability and a higher mass activity than those of Pd/C, PdSn and PdW, respectively. This work not only offers novel insights to strategically design highly efficient electrocatalysts for ethanol oxidation, but also further clarifies the inherent structure‐activity relationship.

Composite combustion behaviors of tubular flame and central jet flame in a reduced-diameter vortex combustor

The characteristics of the tubular flame and the flow field mixing mechanism in a reduced-diameter vortex combustor are investigated by varying the fuel flow rate and equivalence ratio through experiments and numerical simulations. Single-layer tubular flame and double-layer composite tubular flame are found in the combustor under the coupling effect of the cyclone and the central jet. The composite tubular flame will be formed when the air in the combustor is more abundant (Ф>1.00), and the center flame frequency is linearly and positively correlated with the Reynolds number of the central jet air. When the Reynolds number exceeds 2000, the double-layer composite flame tends to stabilize, with the center flame frequency higher than 9 Hz. The turbulence of the central jet air promotes the mixing of reactants by enhancing the recirculation near the nozzle, guaranteeing the central flame's stable combustion. Through analysis of the burn rate of methane at the outlet and the emission species of CO and CO2, it is evident that the double-layer flame achieves the methane burn rate exceeding 95 %, while also exhibiting lower CO emissions compared to the single-layer flame.

H and CO Co-Induced Roughening of Cu Surface in CO2 Electroreduction Conditions.

The dynamic restructuring of Cu has been observed under electrochemical conditions, and it has been hypothesized to underlie the unique reactivity of Cu toward CO2 electroreduction. Roughening is one of the key surface phenomena for Cu activation, whereby numerous atomic vacancies and adatoms form. However, the atomic structure of such surface motifs in the presence of relevant adsorbates has remained elusive. Here, we explore the chemical space of Cu surface restructuring under coverage of CO and H in realistic electroreduction conditions, by combining grand canonical DFT and global optimization techniques, from which we construct a potential-dependent grand canonical ensemble representation. The regime of intermediate and mixed CO and H coverage─where structures exhibit some elevated surface Cu─is thermodynamically unfavorable yet kinetically inevitable. Therefore, we develop a quasi-kinetic Monte Carlo simulation to track the system's evolution during a simulated cathodic scan. We reveal the evolution path of the system across coverage space and identify the accessible metastable structures formed along the way. Chemical bonding analysis is performed on the metastable structures with elevated Cu*CO species to understand their formation mechanism. By molecular dynamics simulations and free energy calculations, the surface chemistry of the Cu*CO species is explored, and we identify plausible mechanisms via which the Cu*CO species may diffuse or dimerize. This work provides rich atomistic insights into the phenomenon of surface roughening and the structure of involved species. It also features generalizable methods to explore the chemical space of restructuring surfaces with mixed adsorbates and their nonequilibrium evolution.

Carbon-Rich Plasma-Deposited Silicon Oxycarbonitride Films Derived from 4-(Trimethylsilyl)morpholine as a Novel Single-Source Precursor.

4-(trimethylsilyl)morpholine O(CH2CH2)2NSi(CH3)3 (TMSM) was investigated as a single-source precursor for SiCNO films synthesis. Optical emission spectroscopy of plasma generated from TMSM/He, TMSM/H2, and TMSM/NH3 gas mixtures revealed the presence of N2, CH, H, CN, and CO species. The last two are suggested to be responsible for the lowering of carbon concentration in the films in comparison with the precursor. The refractive index ranged from 1.5 to 2.0, and bandgap varied from 2.0 to 4.6 eV, which pointed that some of the films can be used as antireflective coatings in silicon photovoltaic cell technologies and dielectric layers in electronic devices.

Catalytic pyrolysis of wood dust for monophenol over macroalgal biochar-based catalyst: Effects of activation agents and atmospheres during catalyst synthesis on its performance

After introducing heteroatoms into the carbon material skeleton, the performance of carbocatalyst during catalytic pyrolysis of biomass for monophenol production is significantly improved. Algae, as a carbon source with intrinsic nitrogen content, is well-identified as a suitable raw material for preparing heteroatom-doped carbocatalyst. The present study aimed to investigate the effects of different alkaline activation agents (KOH/NaOH) and gas atmospheres (N2/CO2) during the carbonization-activation synthesis process of macroalgal biochar-based catalysts (MBBCs) on their properties and performances. Characterizations of carbocatalysts were carried out via BET and XPS analyses to investigate the porous structures and surface functional groups. Results showed that CO2, as a weakly oxidizing atmosphere, can promote the formation of porous structure of MBBCs. However, the promotion is not as strong as that of chemical activation agents (KOH/NaOH). Furthermore, KOH can promote the formation of porous structure more strongly than NaOH, but NaOH can substantially enhance the formation of surface oxygen‑nitrogen groups compared to KOH. All the MBBCs exhibited the increment of monophenols in the bio-oil obtained from catalytic pyrolysis of wood dust, especially phenol, o-cresol, and p-cresol. Amongst, the biochar-based catalyst activated with NaOH in CO2 atmosphere was the most effective one in promoting monophenols content (up to 59.46 %). Compared with the control group (without catalyst), the phenol content was increased from 5.03 % to 19.40 %. Moreover, it is found that the catalytic performance was positively correlated with the CO species percentage on the surface of MBBCs. The macroalgal biochar-based catalyst has an excellent catalytic performance, which is of great significance for achieving the complete utilization of algae and thereby improving the quality of catalytic pyrolysis products.

Operando Raman spectroscopy uncovers hydroxide and CO species enhance ethanol selectivity during pulsed CO2 electroreduction

Pulsed CO2 electroreduction (CO2RR) has recently emerged as a facile way to in situ tune the product selectivity, in particular toward ethanol, without re-designing the catalytic system. However, in-depth mechanistic understanding requires comprehensive operando time-resolved studies to identify the kinetics and dynamics of the electrocatalytic interface. Here, we track the adsorbates and the catalyst state of pre-reduced Cu2O nanocubes ( ~ 30 nm) during pulsed CO2RR using sub-second time-resolved operando Raman spectroscopy. By screening a variety of product-steering pulse length conditions, we unravel the critical role of co-adsorbed OH and CO on the Cu surface next to the oxidative formation of Cu-Oad or CuOx/(OH)y species, impacting the kinetics of CO adsorption and boosting the ethanol selectivity. However, a too low OHad coverage following the formation of bulk-like Cu2O induces a significant increase in the C1 selectivity, while a too high OHad coverage poisons the surface for C-C coupling. Thus, we unveil the importance of co-adsorbed OH on the alcohol formation under CO2RR conditions and thereby, pave the way for improved catalyst design and operating conditions.

Cascade Self-Generation of Carbon Monoxide Triggered by Photoinduced Holes for Efficient Hypoxic Tumors Therapy.

It still remains challenging to design multifunctional therapeutic reagents for effective cancer therapy under a unique tumor microenvironment including insufficient endogenous H2O2 and O2, low pH, and a high concentration of glutathione (GSH). In this work, a CO-based phototherapeutic system triggered by photogenerated holes, which consisted of ionic liquid (IL), the CO prodrug Mn2(CO)10, and iridium(III) porphyrin (IrPor) modified carbonized ZIF-8-doped graphitic carbon nitride nanocomposite (IL/ZCN@Ir(CO)), was designed for cascade hypoxic tumors. Upon light irradiation, the photogenerated holes on IL/ZCN@Ir(CO) oxidize water into H2O2, which subsequently induces Mn2(CO)10 to release CO. Meanwhile, IrPor can convert H2O2 to hydroxyl radical (•OH) and subsequent singlet oxygen (1O2), which further triggers CO release. Moreover, the degraded MnO2 shows activity for glutathione (GSH) depletion and mimics peroxidase, leading to GSH reduction and •OH production in tumors. Thus, this strategy can in situ release high concentrations of CO and reactive oxygen species (ROS) and deplete GSH to efficiently induce cell apoptosis under hypoxic conditions, which has a high inhibiting effect on the growth of tumors, offering an attractive strategy to amplify CO and ROS generation to meet therapeutic requirements in cancer treatment.

Quasi-equilibrium chemical evolution in starless cores

ABSTRACT The chemistry of H2O, CO, and other small molecular species in an isolated pre-stellar core, L1544, has been assessed in the context of a comprehensive gas-grain chemical model, coupled to an empirically constrained physical/dynamical model. Our main findings are (i) that the chemical network remains in near equilibrium as the core evolves towards star formation and the molecular abundances change in response to the evolving physical conditions. The gas-phase abundances at any time can be calculated accurately with equilibrium chemistry, and the concept of chemical clocks is meaningless in molecular clouds with similar conditions and dynamical time-scales, and (ii) A comparison of the results of complex and simple chemical networks indicates that the abundances of the dominant oxygen and carbon species, H2O, CO, C, and C+ are reasonably approximated by simple networks. In chemical equilibrium, the time-dependent differential terms vanish, and a simple network reduces to a few algebraic equations. This allows rapid calculation of the abundances most responsible for spectral line radiative cooling in molecular clouds with long dynamical time-scales. The dust ice mantles are highly structured and the ice layers retain a memory of the gas-phase abundances at the time of their deposition. A complex (gas-phase and gas-grain) chemical structure therefore exists, with cosmic-ray induced processes dominating in the inner regions. The inferred H2O abundance profiles for L1544 require that the outer parts of the core and also any medium exterior to the core are essentially transparent to the interstellar radiation field.

Driving an ecological transformation: unleashing multi-objective optimization for hydrogenated compressed natural gas in a decarbonization perspective.

Integrating hydrogen with CNG is crucial for carbon neutrality and environmental goals, as it enhances flame temperature, reduces emissions, and combats global warming. This study employs the CHEMKIN tool to examine combustion characteristics, including adiabatic flame temperature, mole fraction, normalization, and production rate, in H2-CNG mixtures under various atmospheric and operating conditions. Blending 50% hydrogen with CNG results in significant changes, including a temperature increase from 2322 to 2344 K when the hydrogen content is at 50%. The introduction of hydrogen causes a notable 30-35% reduction in CH4 mole fraction and a simultaneous 26.6% increase in C-normalized CH4 production. Free radicals play a role in affecting CO2 production, with the normalization of CO species increasing from 0.068 to 0.087. Through NSGA-II multi-objective optimization methods, the study identifies a 50% H2-50% CNG blend as the optimal choice for thermal and environmental performance. The study explores the energy and environmental impacts of incorporating hydrogen into CNG-air combustion, with a specific focus on the effects of 50% H2 blending with CNG. Hydrogen blending benefits from elevated adiabatic flame temperature and increased free radical formation, ultimately leading to emission reduction. These findings firmly establish H2-CNG mixtures as promising environmentally friendly alternatives with superior combustion characteristics. Their potential paves the way for significant progress towards achieving carbon neutrality and combating climate change through cleaner, more efficient fuel options.

Multiscale Investigation of the Mechanism and Selectivity of CO2 Hydrogenation over Rh(111).

CO2 hydrogenation over Rh catalysts comprises multiple reaction pathways, presenting a wide range of possible intermediates and end products, with selectivity toward either CO or methane being of particular interest. We investigate in detail the reaction mechanism of CO2 hydrogenation to the single-carbon (C1) products on the Rh(111) facet by performing periodic density functional theory (DFT) calculations and kinetic Monte Carlo (kMC) simulations, which account for the adsorbate interactions through a cluster expansion approach. We observe that Rh readily facilitates the dissociation of hydrogen, thus contributing to the subsequent hydrogenation processes. The reverse water-gas shift (RWGS) reaction occurs via three different reaction pathways, with CO hydrogenation to the COH intermediate being a key step for CO2 methanation. The effects of temperature, pressure, and the composition ratio of the gas reactant feed are considered. Temperature plays a pivotal role in determining the surface coverage and adsorbate composition, with competitive adsorption between CO and H species influencing the product distribution. The observed adlayer configurations indicate that the adsorbed CO species are separated by adsorbed H atoms, with a high ratio of H to CO coverage on the Rh(111) surface being essential to promote CO2 methanation.

Effect of surface species on the alcohol-acid adsorption from FTS wastewater on graphene: A structure-capacity study

Fischer-Tropsch synthesis (FTS) wastewater retaining low-carbon alcohols and acids are organic pollutants as a limiting factor for FTS industrialization. In this work, the structure-capacity relationships between alcohol-acid adsorption and surface species on graphene were reported, shedding light into their intricate interactions. The graphene oxide (GO) and reduced graphene oxide (rGO) were synthesized via improved Hummers method with flake graphite (G). The physicochemical properties of samples were characterized via SEM, XRD, XPS, FT-IR, and Raman. The alcohol-acid adsorption behaviors and adsorption quantities on G, GO, and rGO were measured via theoretical and experimental method. It was revealed that the presence of COOH, C=O and CO species on graphene occupy the adsorption sites and increase the interactions of water with graphene, which are unfavorable for alcohol-acid adsorption. The equilibrium adsorption quantities of alcohols and acids grow in pace with carbon number. The monolayer adsorption occurs on graphene was verified via model fitting. rGO has the highest FTS modeling wastewater adsorption quantity (110 mg/g) due to the reduction of oxygen species. These novel findings provide a foundation for the alcohol-acid wastewater treatment, as well as the design and development of high-performance carbon-based adsorbent materials.

Evolution of Co Species in CO2-Assisted Ethane Dehydrogenation: Competing Cleavage of C–H and C–C Bonds

Evolution of Co Species in CO₂-Assisted Ethane Dehydrogenation: Competing Cleavage of C–H and C–C Bonds

The performance and mechanism of HCHO oxidation on Pd/SiO2 catalysts with different Pd particle sizes

In general, for Pd-based catalysts, the smaller the Pd particles on the catalysts are, the better the activity for HCHO oxidation; this has solely been ascribed to the high Pd dispersion on the catalysts’ surface. However, the Pd site effect on HCHO oxidation is still not clear. In this work, we regulated the proportions of different Pd sites on Pd/SiO2 catalysts by high-temperature treatment of the carriers. With the increase in treatment temperature, the dominant active sites on Pd particles changed from terraces to steps and finally to corner sites. The corner sites were found to be important for oxygen activation, which led to the HCHO catalytic oxidation performance increasing in the order Pd/SiO2, Pd/SiO2(500) and Pd/SiO2(800). It is worth noting that in the reaction pathway for HCHO oxidation, formate was the primary intermediate on the Pd/SiO2 catalyst. However, in addition to formate, CO species were also detected on the Pd/SiO2(500) and Pd/SiO2(800) catalysts. DFT results confirmed that the corner sites were more favorable for the HCHO → CHO → CO pathway, compared to the terrace sites. This work elucidates the effect of Pd sites on the HCHO oxidation mechanism over Pd/SiO2 catalysts, providing valuable insights for the design of highly active catalysts.