Anchoring Pd Nanoparticles Research Articles

Programmable Oxygen Reduction Reaction Performance of Atomic Ir-Clusters Anchored Pd Nanoparticles on the Ni-Oxide Support

Fuel cells is severely restricted by the sluggish oxygen reduction reaction (ORR) kinetics at the cathode side, which demands highly active and enduring catalysts for producing adequate rates. Herein, we report a systematic study to investigate the effect of structure configuration on the oxygen reduction reaction (ORR) activity of tri-metallic nanocatalysts (NC)s comprising atomic Ir-clusters (0.5 wt.% of Ir) anchored Pd nanoparticles on the tetrahedral symmetric Ni-oxide support (denoted as NPI). The electrochemical activities of NPI NCs are programmable via a temperature-controlled wet chemical reduction method. For the optimum condition when the Ni-crystal impregnation temperature is 40oC, the Ir-clusters decorated Ni@Pd nanoislands are formed (hereafter denoted as NPI-40), outperforming the commercial J.M.-Pt/C (20 wt.% Pt) catalyst by ~180-folds with an unprecedented high mass activity of ~12,000 mAmgIr -1 at 0.85 V vs RHE in 0.1 M KOH. More importantly, NPI-40 NC retained 100 % ORR performance with no degradation up to 20k accelerated degradation test cycles, while only a 5 mV loss in half-wave potential (E1/2 ) is observed after 30k ADT cycles. The results of physical structure inspections and electrochemical analysis suggest that such an exceptional ORR performance of NPI-40 NC originates from the potential synergetic effect between the high density of occupied Ir-d-orbital and adjacent compressively strained Ni-Pd interface. With this structure configuration, Ir-sites offer optimal adsorption energy for O2 splitting and Ni-Pd interface facilitates the subsequent desorption of hydroxide ions (OH-). We believe that the obtained results will open new approach for the design of Pt-free NCs for fuel cell cathode. Keywords: Oxygen reduction reaction, Fuel cells, Mass activity, Ir clusters

Synthesis of Pd/Carbon Hollow Spheres by the Microwave Discharge Method for Catalytic Debenzylation.

Pd/C catalysts have been widely applied in the debenzylation process due to their excellent ability of hydrogenolysis. However, they have been suffering from the problems of agglomeration and loss of active components, which lead to decreased and unstable activity. Thus, it is still a challenge to achieve Pd/C catalysts with high activity and stability. Herein, we propose a strategy for preparing Pd/C catalysts on porous carbon hollow spheres by a microwave discharge method. Due to the high-temperature property and reducibility of microwave discharge, Pd precursors can be rapidly reduced, resulting in well-dispersed Pd nanoparticles with a small size on the carbon carrier. Besides, the matched mesopores in the carbon hollow spheres can anchor Pd nanoparticles and effectively reduce the agglomeration and loss of Pd nanoparticles during the catalytic reaction. As a result, the as-prepared Pd/mesoporous carbon hollow spheres exhibit high and stable activity in the debenzylation reaction.

N-Doped graphene fiber anchored Pd nanoparticles as a fixed-bed catalyst for continuous-flow reduction of N-containing unsaturated compounds

Catalytic fixed-bed is an efficient and facile system for scalable organic synthesis due to its continuous and fast flow operation process. As a key unit in the fixed-bed system, catalytically active packing materials are required to possess some properties, such as high activity, excellent stability, and porous packing structure. Herein, we prepare a fibrous fixed-bed catalyst by anchoring Pd nanoparticles on N-doped graphene fiber (NHG) (Pd/NGF). Due to the porous and loose packing structure, the resultant Pd/NGF catalyst can be easily filled into the continuous-flow reactor to construct a fixed-bed system with low flow resistance. The corresponding catalytic fixed-bed system exhibits a favourable flow rate (8 ​mL/min) and excellent durability toward reduction reactions of N-containing unsaturated compounds to produce aromatic amines. This work provides a new design concept of fibrous fixed-bed catalysts with dual-active components (i.e., graphene-derived active materials and metal nanoparticles) and catalytic organic synthesis in a continuous-flow process.

N-doped hollow carbon nanospheres anchored Pd NPs for mild selective hydrodeoxygenation of bio-models

Hydrodeoxygenation (HDO) is a promising approach for the synthesis of renewable fuels and chemicals, while the design and preparation of high-performance catalysts in this field remain a challenge. Herein, a series of hollow carbon nanospheres anchored Pd nanoparticles (NPs) catalysts with different nitrogen doping contents (Pd/HCAFR-X, X=0.3, 0.6, 0.9) were prepared for the selective HDO of bio-models compound under mild conditions. Notably, the Pd/HCAFR-0.6 catalyst exhibited excellent catalytic performance for the acetophenone (APh) HDO in polymethylhydrosiloxane (PMHS) at 50 °C for 3 h, and the yield of ethylbenzene was close to 99%. The good catalytic results can be mainly attributed to the unique hollow carbon nanospheres with abundant defects provided by appropriate nitrogen doping content. The large surface area and hierarchical porous structure of the hollow carbon framework offered more active sites, which promoted the transportation of species on the catalyst. In addition, the nitrogen doping amount can adjust the defect degree of the hollow carbon nanospheres, stabilize the dispersion and anchoring of Pd NPs, and then induce the transfer of local electrons. Furthermore, the Pd/HCAFR-0.6 catalyst showed good catalytic performance for bio-models compound HDO after 5 cycles.

Configuration-Dependent Oxygen Reduction Reaction Performance of Iridium-Decorated Ni@Pd Nanocatalysts

The widespread market introduction of fuel cells is severely restricted by the sluggish oxygen reduction reaction (ORR) kinetics at the cathode side, which demands highly efficient and durable catalysts for generating adequate rates. By keeping this in view, herein, we report a systematic study to unveil the effect of structure configuration on the ORR activity of tri-metallic nanocatalysts (NC)s comprising atomic iridium (Ir) cluster (0.5 wt % of Ir)-anchored Pd nanoparticles (NP)s on the tetrahedral symmetric Ni-oxide support (denoted as NPI), prepared via a temperature-controlled wet chemical reduction method. For the optimum condition when the impregnation temperature for Ni-crystal growth is 40 °C, the Ir-cluster-decorated Ni@Pd nanoislands are formed (hereafter denoted as NPI-40), outperforming the commercial Johnson Matthey-Pt/C (J.M.-Pt/C; 20 wt % Pt) catalyst by 181-fold with an unprecedented high mass activity of 12,163 mAmgIr–1 at 0.85 V vs RHE in alkaline ORR (0.1 M KOH). More importantly, NPI-40 NC retained 100% ORR performance with no degradation up to 20,000 accelerated degradation test (ADT) cycles, while only a 5 mV loss in half-wave potential (E1/2) is observed after 30 k ADT cycles. Besides, Ir-cluster-decorated Nicore@unconformable Pdshell and Ni-to-Pd epitaxial structures are formed at 25 °C (NPI-RT) and 70 °C (NPI-70) impregnation temperatures, respectively, showing the significantly decreased mass activities of 997 and 5146 mAmgIr–1 at 0.85 V vs RHE. The results of physical structure inspections and electrochemical analysis suggest that such an exceptional ORR performance of NPI-40 NC originates from the potential synergism between the high density of the occupied Ir-d orbital and the adjacent compressively strained Ni–Pd interface, where Ir sites offer optimal adsorption energy for O2 splitting and the Ni–Pd interface facilitates the subsequent desorption of hydroxide ions (OH–). We believe that the obtained results will open new avenues for the facile design of Pt-free NCs for fuel cell cathodes and will benefit fuel-cell technology via both ecologically and economically friendly means.

Continuous Flow Liquid‐Phase Semihydrogenation of Phenylacetylene over Pd Nanoparticles Supported on UiO‐66(Hf) Metal‐Organic Framework

AbstractCatalysis under continuous flow operation is industrially more relevant compared to reactions carried out in batch reactors. But catalysis with metal‐organic frameworks (MOFs) is largely restricted to batch reactions, especially in case of semi hydrogenation reactions. We anchored Pd nanoparticles (NPs) on robust UiO‐66(Hf) MOF to develop effective catalyst for semi hydrogenation of phenylacetylene into styrene. We investigated catalytic performance of Pd/UiO‐66(Hf) in a continuous‐flow liquid‐phase semi‐hydrogenation of phenylacetylene (PA). In this study, Pd/UiO‐66(Hf) catalyst exhibited good catalytic performance with a rare combination of high PA conversion (99.0 %) and high styrene selectivity (90.0 %). Additionally, Pd/UiO‐66(Hf) demonstrated lower deactivation rate in contrast to many reported materials to date. The higher stability of metal NPs over UiO‐66(Hf) aroused from the strong metal‐support interaction (between Brønsted acidic μ3‐OH of MOF and Pd). The Pd/UiO‐66(Hf) retained its catalytic activity even after four recycles.

Organic Heterocyclic Strategy for Precisely Regulating Electronic State of Palladium Interface to Boost Alcohol Oxidation

AbstractExploring highly‐efficient palladium (Pd)‐based electrocatalysts for the alcohol oxidation reaction (AOR) is crucial yet challenging for chemists due to the vague Pd interface with an uncontrollable electronic environment. Herein, an organic heterocyclic strategy is used for the first time to modulate the electronic state of Pd electrocatalysts by anchoring Pd nanoparticles to conjugated microporous polymers (CMPs) with varied S‐, N‐, O‐, or S, N‐heterocycles. Among these CMPs, the S, N‐containing thiazole heterocyclic polymer SNC with Pd catalyst exhibits highly‐efficient current densities of 1575.0 mA mgPd−1 for methanol oxidation and 1071.0 mA mgPd−1 for ethanol oxidation, which are among the highest performance in the heterocyclic modulated Pd systems and surpass the commercial Pd black catalyst. Detailed theory calculations suggest that although the furan (O‐heterocycle) polymer OC has the strongest charge transfer (0.057 |e|) with the Pd cluster, the moderate electron transfer (0.041 |e|) of the Pd/SNC heterojunction with an S···N···Pd noncovalent interaction shows the best catalytic reaction kinetics. Moreover, the d‐band of the Pd/SNC system is closer to the volcano vertex than its counterparts. These results indicate that appropriate electron transfer intensity regulation of Pd electronic state by well‐defined heterocyclic structures may significantly improve AOR activity.

Anchoring Pd Nanoparticles with Low Loading on Co,N‐Doped Carbon Framework for the Synergistic Reduction of Nitrophenols

AbstractThe reduction of nitro‐compound to amino‐compound through catalytic transfer hydrogenation over Pd‐based nanostructured composites is an attractive issue. Herein, a series of nanocomposites including Pd nanoparticles with low weight loading anchored on N, Co‐doped carbon framework (Co@NC) was prepared by a facile method. Among these, 1.5 % Pd/Co@NC had the highest catalytic activity towards the reduction of nitrophenols. The enhanced activity may be ascribed to N‐doping, synergistic effect and the interaction between well‐dispersed Pd nanoparticles and N, Co‐doped carbon framework by stabilizing metal nanoparticles with smaller size and good dispersion, improving the adsorption of reactants on the surface of Pd/Co@NC and facilitating electron transfer from NaBH4 to the product. Furthermore, the catalyst maintained regular morphology and activity even after recycling experiments, indicating that it may be used in industrial applications.

Oxygen vacancies endow atomic cobalt-palladium oxide clusters with outstanding oxygen reduction reaction activity

Considering the technological importance of fuel cells, developing highly efficacious, durable, and Platinum (Pt)-free catalysts are crucial. In this work, we propose a novel nanocatalyst (NC) comprising oxygen vacancies (OV) enriched atomic CoPdOx clusters (CoPdOxV) anchored Pd nanoparticles (NP)s on cobalt-oxide support (denoted as CPCo). As-prepared CPCo NC with an additional 3 wt% of Co decoration (denoted as CPCo-3) delivers an exceptionally high mass activity (MA) of 4394 mAmgCo−1 at 0.85 V vs RHE and 426 mAmgCo−1 at 0.90 V vs RHE in alkaline oxygen reduction reaction (ORR) (0.1 M KOH), which surpasses the commercial J.M.-Pt/C (20 wt%) catalyst by 65-times. More importantly, the CPCo-3 NC exhibits outstanding durability in an accelerated durability test (ADT) with a progressively increased MA by 40 % (6,140 mAmgCo−1) as that of the initial condition after 20 k cycles. Through in-depth physical characterization, electrochemical analysis, and in-situ X-ray absorption spectroscopy (XAS), we demonstrated the conceptual framework of potential synergism between the CoPdOxV and neighbouring metallic Pd-sites. In this event, the surface-anchored CoPdOxV species coupling with OV promotes the O2 splitting, while the neighbouring Pd-sites simultaneously trigger the Oads relocation (i.e. OH− desorption) step. In addition, the cobalt oxide support underneath assists the electron injection to surface Pd-sites. This work not only marks a step ahead for designing high-performance transition metal oxide catalysts for fuel cells but also uncovers the material’s aspects of cobalt that shall spark motivation for the other catalytic applications.

Oxygen vacancy-rich WO3-x/rGO composite supported Pd catalyst for efficient selective hydrogenation of nitroaromatics

The development of efficient catalysts for selective hydrogenation of nitroaromatics to corresponding aromatic amines has significant application requirement. In this study, a novel and effective catalyst was prepared by anchoring Pd nanoparticles on oxygen vacancy-rich tungsten oxide (WO3−x) and reduced graphene oxide (rGO) composite support (Pd-WO3−x/rGO). Owing to the strong metal support interaction (SMSI), which can significantly regulate the d-electronic structure of Pd, the Pd-WO3−x/rGO catalyst showed remarkable catalytic activity and selectivity for the hydrogenation of nitroaromatics. Under the reaction conditions of 100 °C and 1 MPa H2, a 100 % yield was achieved for the selective hydrogenation of p-chloronitrobenzene to p-chloroaniline. The catalyst also delivered excellent reusability, which can be readily recycled for at least 10 times without significant loss of activity. This work provide a feasible avenue for the construction of high-performance catalysts for the selective hydrogenation of nitroaromatics and beyond.

Hybrid Composite of Subnanometer CoPd Cluster-Decorated Cobalt Oxide-Supported Pd Nanoparticles Give Outstanding CO Production Yield in CO2 Reduction Reaction

Catalytic carbon dioxide (CO2) hydrogenation to carbon monoxide (CO) via reverse water-gas shift (RWGS) reaction is of particular interest due to its direct use in various industrial processes as feedstock. However, the competitive CO2 methanation process severely limits the RWGS reaction in a lower temperature range. In this context, we propose a novel nanocatalyst (NC) comprising oxygen vacancy-enriched subnanometer-scale CoPd hybrid cluster (CoOxVPd)-anchored Pd nanoparticles (NPs) on cobalt oxide support underneath (denoted as CP-CoOxVPd) by using a galvanic replacement reaction-assisted wet chemical reduction method. As-developed CP-CoOxVPd NC initiated the RWGS reaction at 423 K temperature while showing an optimum CO production yield of ∼3414 μmol g−1catalyst and a CO selectivity as high as ∼99% at 523 K in the reaction gas of CO2:H2 = 1:3. The results of physical characterizations along with electrochemical and gas chromatography (GC) suggest that abundant oxygen vacancies in the surface-anchored CoOxVPd clusters are vital for CO2 adsorption and subsequent activation, while neighboring Pd domains facilitate the H2 dissociation. The obtained results are expected to provide a feasible design of Co-based NCs for the RWGS reaction.

Unveiling the effect of gas treatment on the electronic structure of carbon nanotube-supported Pd catalysts for electroreduction of H2O2 and Heck reaction

This study explored the impact of gas treatments on the structures of multi-walled carbon nanotubes supported Pd (CNT-Pd) catalysts used for electrocatalytic H2O2 reduction and the Heck cross-coupling reaction. The CNT-Pd catalyst was prepared by anchoring Pd nanoparticles on thiolated CNTs. XPS was conducted to examine the surface composition and electronic structure changes of the CNT-Pd catalyst before and after gas treatment. The XPS results revealed that as-prepared CNT-Pd contains at least two different oxidation states on the surface, whereon their proportions depend on the gas used for treatment. Treatment with H2 leads to Pd(0) enrichment near the surface, while O2 treatment causes Pd(Ⅱ) enrichment of CNT-Pd. All catalysts containing both Pd(0) and Pd(Ⅱ) were active toward H2O2 reduction, and the Heck cross-coupling reaction of n-butyl acrylate and 4-iodotoluene; increased proportion of metallic Pd(0) boosted the catalytic reaction. However, the catalyst stability increased as the amount of Pd(II) increased.

Catalytic transfer hydrogenation of nitrobenzene over Ti3C2/Pd nanohybrids boosted by electronic modification and hydrogen evolution inhibition

Catalytic transfer hydrogenation (CTH) with formic acid attracts much interest in catalysis, but the sluggish H* production and undesirable H2 evolution reaction (HER) limit its practical applications. Herein we anchored Pd nanoparticles (NPs) on layered Ti3C2 MXene for efficient and selective CTH of nitrobenzene in the presence of formic acid. Some electrons in Pd NPs transferred to Ti3C2 MXene upon formation of Ti3C2/Pd nanohybrids, as confirmed by XPS and DFT simulations. The electron transfer changed Pd valance electron configuration from 4d10 to 4d10-x. Such electron-deficient Pd NPs tuned reaction pathway and promoted formic acid dissociation, both of which favored the production of active H* atoms, i.e., the exact reductant for CTH. Compared with Pd NPs, Ti3C2/Pd showed stronger adsorption of H* and therefore inhibited the occurrence of HER (2H*→H2). Owing to favorable H* production and HER inhibition, Ti3C2/Pd (15 wt% Pd) showed enhanced nitrobenzene CTH performance with turnover frequency of 351.7 h−1 and 99% aniline selectivity, outperforming most of current catalysts. Our work might inspire designing more advanced CTH catalysts by tuning their valance electron configurations with 2D MXene materials.

Defective N‐Doped Carbon Nanospheres Anchored Pd for Selective Hydrodeoxygenation of Bio‐Models under Mild Conditions

Hydrodeoxygenation (HDO) is of great significance in converting biomass into high value‐added chemicals under mild conditions. However, the design of effective catalysts remains challenge. Herein, a N‐doped carbon nanospheres–supported Pd catalyst for mild vanillin HDO is designed by defect‐enhancement engineering using in situ synthesis. According to the characterization results, the degree of defects is enhanced on the in situ N‐doped carbon spheres (CAFR) with 3‐aminophenol as nitrogen source, which is related to the higher content of pyridine nitrogen. The Pd/CAFR with the most degree of defects exhibits excellent catalytic performance (99.8% of 2‐methoxy‐4‐methylphenol yield) at 50 °C. The plentiful defects act as active sites for anchoring Pd nanoparticles (NPs) to promote uniform dispersion. Meanwhile, the highly dispersed Pd NPs are coordinated with abundant defects through strong metal‐support interaction to increase the content of reduced Pd NPs, which improves the catalytic activity under mild conditions. Moreover, the optimal Pd/CAFR catalyst shows favorable recyclability after five cycles. The defect‐enhancement engineering on carbon materials by in situ N‐doping provides a new idea for support modification of high‐efficiency catalysts under mild conditions.

Engineering of N,P,S-Triple doped 3-dimensional graphene architecture: Catalyst-support for “surface-clean” Pd nanoparticles to boost the electrocatalysis of ethanol oxidation reaction

The engineering of robust electrocatalysts for the ethanol oxidation reaction (EOR) with cost-natural, superior electrocatalytic activity, and stability, is crucial for the scaled-up applications of direct ethanol fuel cells. Herein, a facile bottom-up hydrothermal strategy has been implemented to synthesize N,P,S triple-doped 3-dimensional (3D) graphene architectures (N,P,S-3DG) with interconnected, hierarchical porous structure, followed by Pd nanoparticles were uniformly decorated onto the N,P,S-3DG via solvothermal approach. As fabricated hybrid nanocatalyst, labeled as Pd@N,P,S-3DG, is of charming physicochemical characteristics including large electrochemically active specific surface area, interconnected hierarchical pore network, a satisfactory percentage of heteroatom dopants, uniform distribution of Pd nanoparticles, as well as superior electrocatalytic performance metrics such as high catalytic activity, long-term stability, and tolerance to poisoning. The characterizations have confirmed the strong electrostatic interaction between the Pd nanoparticles and carbonaceous support material, thereby leading to homogeneously anchoring Pd nanoparticles onto 3D architecture and forming of novel active sites as well as synergistically boosting the EOR catalytic activity. The Pd@N,P,S-3DG has offered an enlarged electrochemically active surface area (50.3 m2 g−1), an enhanced catalytic current density of 1784 mA mg−1Pd, and outstanding long-term stability, thereby distinctly transcending those of commercial carbonaceous material-supported Pd catalysts. The work is of great importance since it may pave the way for the rational design of low-cost high-performance carbonaceous-based nano-electrocatalysts to be utilized in large-scale energy applications.

Anchoring Pd nanoparticles on hollow CuS nanoparticles for enhanced NIR induced photothermal effects for chemotherapeutic drug delivery and gastric cancer treatment

Traditional cancer chemotherapy has resulted in nonspecific drug delivery, low cellular anticancer drug uptake, and severe side effects to normal tissues. Near-infrared (NIR)-responsive photothermal therapy has emerged as a new non-invasive cancer treatment with more controllable drug delivery, higher anticancer efficacy, and reduced side effects. Noble metal nanomaterials possess superior photothermal and optical properties, but the high cost and scarcity limit their applications in biomedical fields. Herein, we reported the synthesis of Pd nanoparticles anchored hollow CuS nanospheres (CuS/Pd composite) as drug carriers for NIR-induced drug delivery and cancer treatment. The CuS/Pd composite shows significantly enhanced photothermal properties in comparison with CuS. The cytotoxicity test indicates the high biocompatibility of CuS/Pd. Notably, the NIR-triggered effective and controllable release of loaded doxorubicin (DOX) under NIR laser irradiation is successfully demonstrated. A series of cell viability experiments show that the survival rate of cancer cells with CuS/Pd/TD/DOX is as low as ∼20%. In addition, the CuS/Pd composite exhibits excellent material stability. Therefore, this work sheds light on the design and synthesis of low-cost and effective drug carriers for enhanced NIR-induced drug delivery and cancer treatment.

Defect-rich ZrO2 anchored Pd nanoparticles for selective hydrodeoxygenation of bio-models at room temperature

The hydrodeoxygenation (HDO) of biomass-derived compounds into high-quality fuels and chemicals is an effective solution to the fossil energy shortage. However, the development and design of catalysts with high-performance HDO under mild reaction conditions is a significant challenge. In this paper, the defect-rich ZrO2 anchored Pd nanoparticles was investigated for selective HDO of bio-models at room temperature. The oxygen vacancies of Pd/ZrO2(x) catalysts can be regulated by the addition of template agent cetyltrimethylammonium bromide (CTAB), in which CTAB combines with OH on the support to form complex oxides and then promoting the formation of Zr3+-Ov-Zr4+ structure of the as-prepared Pd/ZrO2(x) catalysts. When the mass ratio of CTAB/ZrOSO4 is 0.5, the Pd/ZrO2(0.5) catalyst with the highest oxygen defect content exhibits excellent performance towards 99.9% yield of 2-methoxy-4-methylphenol (MMP) at 25 °C for one hour in vanillin HDO. The rich oxygen vacancies of Pd/ZrO2(x) catalysts can regulate the electronic structure of the catalyst surface metal palladium and zirconium, and promote the adsorption and hydrogenolysis of C-O in vanillin HDO. In addition, it is obviously that the catalysts had excellent versatility and stability, and the MMP selectivity of the Pd-ZrO2(0.5) catalyst slightly decreased after five consecutive reactions.

Highly Active and Stable Fe/Co/N Co-doped Carbon-Anchored Pd Nanoparticles for Oxygen Reduction Reaction.

A highly active and stable electrocatalyst based on Pd nanoparticles anchored on zeolitic imidazolate framework-derived Fe/Co/N co-doped carbon (Pd/FeCoNC) is prepared. FeCo alloy nanoparticles are uniformly dispersed and wrapped by graphene layers in Fe/Co/N co-doped carbon (FeCoNC). The influences of carbonization temperature on the structure and catalytic activity of FeCoNC toward oxygen reduction reaction (ORR) are investigated. The FeCoNC prepared at 800 °C (FeCoNC-800) has a favorable ORR catalytic activity as a consequence of the synergistic effect of Fe/Co/N co-doping and hierarchical pore structures of coexisting micropores and mesopores. Pyridinic N in FeCoNC is a preferential adsorption site for anchoring Pd nanoparticles. Pd/FeCoNC exhibits both superior activity and durability to 40 wt % Pt/C at the same level of metallic mass loading, which shows a 44 mV higher half-wave potential (0.88 V) than Pt/C and a 91% remaining current of the initial after 10,000 s. The Fe/Co/N co-doping and hierarchical pores of FeCoNC contribute a large diffusion current, and the introduction of Pd realizes more positive onset and half-wave potentials. This work provides an easy way for preparing low-cost and high-efficiency catalysts for ORR.

Pd/CNT with controllable Pd particle size and hydrophilicity for improved direct synthesis efficiency of H2O2

Comparison of Pd catalyst performance before and after N/O doping. Schematic diagram of anchoring Pd nanoparticles on the surface of N and O doped CNT.

Catalytic Activity Analysis of Uniform Palladium Nanoparticles Anchored on Nitrogen-Doped Mesoporous Carbon Spheres for Oxygen Reduction Reaction

Palladium (Pd)-based catalysts, as an ideal alternative to platinum (Pt) for oxygen reduction reaction (ORR), have been the focus of recent research because of their comparable catalytic activities, low cost, and abundant resource. Unfortunately, Pd is easy to suffer from agglomeration because of the decrease of their excessive metal surface free energy at elevated temperature, dramatically reducing their catalytic activities for ORR. Herein, we report a facile in-situ self-assembly strategy coupled with the annealing method to synthesize the well-dispersed Pd nanoparticles on nitrogen-doped mesoporous carbon spheres (Pd-NMCS) catalysts, and analyze the catalytic activities for ORR. More importantly, the nitrogen atoms in the NMCS can expose more basic/catalytic sites that can coordinate with Pd nanoparticles to form the strong Pd-N interactions, which can not only tightly anchor Pd nanoparticles but also be advantageous to show outstanding stability and good resistance to methanol crossover. As expected, the obtained Pd-NMCS exhibit good ORR catalytic activities, desirable reaction kinetics, excellent stability, as well as better methanol tolerance, which may offer potential for the practical application of fuel cells. The existence of strong Pd-N interaction enables the Pd nanoparticles to uniformly disperse on the NMCS (Pd-NMCS), thus achieving good ORR catalytic activities, desirable reaction kinetics, outstanding stability as well as better tolerance to methanol crossover of the Pd-NMCS catalyst in the alkaline condition.