Optimized Synthesis of Nitrogen and Phosphorus Dual-Doped Coal-Based Carbon Fiber Supported Pd Catalyst with Enhanced Activities for Formic Acid Electrooxidation

Highly dispersed palladium nano-catalyst anchored on N-doped nanoporous carbon microspheres derived from chitosan for efficient and stable hydrogenation of quinoline

Under the background of green chemistry, the synthesis of N-heterocycles using efficient, stable and long-life catalysts has still faced great challenges. Herein, we used biomass resource chitosan to fabricate a nanoporous chitosan carbon microsphere (CCM), and successfully designed a stable and efficient Pd nano-catalyst (CCM/Pd). Various physicochemical characterizations provided convincible evidences that the palladium nanoparticles (NPs) were tightly and evenly dispersed on the CCM with a mean diameter of 2.28 nm based on the nanoporous structure and abundant functional N/O groups in CCM. Importantly, the graphitized constructure, the formed defects and larger surface area in CCM were able to promote the immobilization of Pd NPs and the electron transfer between Pd and CCM, thereby significantly improving the catalytic activity. The CCM/Pd catalyst was applied for hydrogenation of quinoline compounds, which showed excellent catalytic activity and durability, as well as good substrate applicability. The application of renewable biomass-based catalysts contributes to the progression of a green/sustainable society.

Construction of Ni2P-MoC/Coal-Based Carbon Fiber Self-Supporting Catalysts for Enhanced Hydrogen Evolution

Efficient and inexpensive electrocatalysts play an important role in the hydrogen evolution reaction (HER) of electrolytic water splitting. Herein, Ni2P-MoC/coal-based carbon fiber (Ni2P-MoC/C-CF) self-supporting catalysts were obtained by low-temperature phosphorization and high-temperature carbonization. The Mo source and oxidized coal were uniformly dispersed in the carbon support by electrospinning technology. A precursor of Ni was introduced by the impregnation method. The synergistic effect of MoC and Ni2P may reduce the strong hydrogen adsorption capacity of pure MoC and provide a fast hydrogen release process. In addition, the C-CFs prepared by electrospinning can not only prevent the agglomeration of MoC and Ni2P particles at a high temperature but also provide a self-supporting support for the catalyst. As a result, the catalytic performance of the HER was improved greatly, and a low overpotential of 112 mV at 10 mA cm-2 was exhibited stably by the Ni2P-MoC/C-CFs. This work not only converts coal into coal-based carbon materials but also provides a feasible pathway for the rational design of large-scale molded hydrogen electrocatalysts.

PdMo Bimetallene Coupled with MXene Nanosheets as Efficient Bifunctional Electrocatalysts for Formic Acid and Methanol Oxidation Reactions

In this study, we demonstrate a facile soft chemistry strategy for the in situ growth of two-dimensional (2D) ultrathin PdMo bimetallene tightly coupled with Ti3C2Tx MXene nanosheets (PdMo/Ti3C2Tx) using a robust stereoassembly process. The 2D PdMo bimetallene offers numerous unsaturated Pd atoms and simultaneously induces combined bimetallic alloy and strain effects, while the Ti3C2Tx matrix effectively optimizes the electronic structure of PdMo bimetallene via a face-to-face interface interaction and guarantees exceptional electrical conductivity. As a consequence, the newly designed PdMo/Ti3C2Tx nanoarchitecture expresses remarkable electrocatalytic properties for the formic acid and methanol electro-oxidation, in terms of large electrochemically active surface areas, ultrahigh catalytic activity, strong antipoisoning ability, and dependable long-term stability, all of which are better than those of conventional Pd nanoparticle catalysts supported by Ti3C2Tx and carbon matrices.

Nitrogen and Phosphorus Dual-Coordinated Single-Atom Mn: MnN2P Active Sites for Catalytic Transfer Hydrogenation of Nitroarenes

The coordination environment of atomically metal sites can modulate the electronic states and geometric structure of single-atom catalysts, which determine their catalytic performance. In this work, the porous carbon-supported N, P dual-coordinated Mn single-atom catalyst was successfully prepared via the phosphatization of zeolitic imidazolate frameworks and followed by pyrolysis at 900 °C. The optimal Mn₁-N/P-C catalyst with atomic MnN₂P structure has displayed better catalytic activity than the related catalyst with Mn-N_x structure in catalytic transfer hydrogenation of nitroarenes using formic acid as the hydrogen donor. We find that the doping of P source plays a crucial role in improving the catalytic performance, which affects the morphology and electronic properties of catalyst. This is the first Mn heterogeneous catalyst example for the reduction of nitroarenes, and it also revealed that the MnN₂P configuration is a more promising alternative in heterogeneous catalysis.

Well-designed internal electric field from nano-ferroelectrics promotes formic acid oxidation on Pd

Pd-Based catalysts are considered the most efficient catalysts in direct formic acid fuel cells. However, the poisoning and dissolution of Pd in acidic systems limit its commercialization. Here, we propose an all-in-one solution for the anti-dissolution and anti-poisoning properties of palladium. A novel structured catalyst, Pd nanoparticles embedded in a carbon layer internally decorated with tourmaline nanoparticles (TNPs), is proposed for formic acid oxidation (FAO). The internal electric field strength of the catalysts is readily regulated by controlling the amount of TNPs. Remarkably, the prepared catalyst exhibits as high as 3.9 times mass activity (905 A g^-1) compared with the commercial Pd/C catalyst. The significant improvement in the electrocatalytic performance of the catalyst is mainly due to the polarized electric field of TNPs causing charge transfer from Pd to tourmaline, which weakens the O-H bond of HCOOH and the bond between Pd and CO_ad. Another advantage brought by the internal polarized electric field is that it facilitates water dissociation to produce OH_ad, thereby improving the anti-poisoning ability of the catalyst in acidic media. Moreover, the firmly anchored Pd nanoparticles can avoid dissolution and agglomeration during long-term use. 80.2% mass activity remained after the accelerated durability test.

Boosting the anti-poisoning ability of palladium towards electrocatalytic formic acid oxidation via polyphosphide chemistry

In this work, we reported a novel polyphosphide strategy for the synthesis of phosphorus doped Pd (P-Pd) using red phosphorus as the starting material at quasi-ambient conditions. Polyphophide anions, as the key reaction intermediates, served as the reducing agent and phosphorus source to modulate the surface electronic structure of Pd. The P-Pd obtained exhibited topmost CO tolerance and electrocatalytic activity to formic acid oxidation among the state-of-arts reports. The mass activity and turnover frequency of P-Pd reached 4413 mA mg^-1_Pd and 16.04 s^-1 at 0.8 V, which were 23.7 and 6.4 times that of commercial Pd/C respectively. After 1000 repeated cycles, 82% initial activity was reserved. Combined with the electrochemical analysis and the density functional theory calculation, the boosted electrochemical performances can be attributed to the size and electronic effects induced by the P doping, which increase the surface actives sites, inhibit the adsorption of CO and change the reaction pathway to favorable CO₂ route. A full cell was also assembled to demonstrate the practical potential of the P-Pd, which showed a maximum power density of 21.56 mW cm^-2. This polyphophide-based reaction route provides a new strategy for the preparation of efficient and durable phosphorus doped alloys for electrocatalysis.

ZIF-8@ZIF-67-Derived Co Embedded into Nitrogen-Doped Carbon Nanotube Hollow Porous Carbon Supported Pt as an Efficient Electrocatalyst for Methanol Oxidation

It is of prime importance to develop anode electrocatalysts for direct methanol fuel cells (DMFCs) with good performance, which is critical for their commercial applications. Metal-organic framework (MOF)-derived carbon materials are extensively developed as supports of catalysts. Herein, Co embedded nitrogen-doped carbon nanotube hollow porous carbon (Co-NCNT-HPC) derived from MOFs have been fabricated, which were synthesized by pyrolyzing at an optimized temperature of 800 °C using ZIF-8@ZIF-67 as a precursor. The presence of ZIF-8@ZIF-67 ensures the doping of nitrogen and the large specific surface area of the support materials at high temperatures. A Pt/Co-NCNT-HPC800 sample, which was synthesized using Co-NCNT-HPC800 as a support, showed an enhanced mass activity of 416.2 mA mg⁻¹_Pt for methanol oxidation reaction (MOR), and the onset potential of CO_ad oxidation of 0.51 V, which shifted negatively about 0.13 V compared with Pt/C (20%). Moreover, the Pt/Co-NCNT-HPC800 sample exhibits high stability. This work provides a facile strategy for MOF-derived carbon materials to construct advanced electrocatalysts for MOR.

Dicyanamide Anion-Based Ionic Liquid-Functionalized Graphene-Supported Pt Catalysts for Boosting Methanol Electrooxidation

As an environmentally friendly energy technology, direct methanol fuel cells (DMFCs) meet the needs of sustainable development. Herein, novel dicyanamide anion-based (N(CN)₂^-) ionic liquid (IL)-functionalized reduced graphene oxide (rGO)-supported Pt catalysts are synthesized via a facile one-pot room temperature reduction method, which show a boost in methanol oxidation performance compared with Pt/rGO. The mass activities of the as-prepared Pt/emimN(CN)₂/rGO (863.6 mA mg^-1_Pt) and Pt/epyN(CN)₂/rGO (524.9 mA mg^-1_Pt) are about five and three times higher than that of Pt/rGO (178.6 mA mg^-1_Pt), and about six and four times higher than that of Pt/C (140.2 mA mg^-1_Pt), respectively. The participation of ILs significantly improves the CO poisoning resistance, stability, and activity for methanol oxidation of catalysts. The relationship between the structures and conductivities of diverse ILs and the performance of Pt catalysts are studied systematically. These findings may offer a promising prospect of ILs in DMFCs.

Enhancement of the performance of Pd nanoclusters confined within ultrathin silica layers for formic acid oxidation

The optimized design of highly active and stable anode electrocatalysts is essential for high performance direct formic acid fuel cells (DFAFCs). Herein, a facile and cost-effective strategy was proposed to fabricate a robust ultrasmall Pd nanocluster confined within ultrathin protective silica layers anchored on nitrogen doped reduced GO (NrGO) through generating amine functionalized graphene oxide with 3-aminopropyl triethoxysilane (APTES), followed by tuning the thickness of protective silica layers by precisely controlling the amount of tetraethylorthosilicate (TEOS). Amine functionalized graphene oxide generated by using APTES favors the formation of ultrasmall Pd nanoclusters due to the coordination of amine to PdCl24- while the confinement effect of ultrathin protective silica layers stabilizes ultrasmall Pd nanoclusters and impedes the agglomeration and sintering of ultrasmall Pd nanoclusters during electrocatalysis. As a result, the ultrasmall Pd nanoclusters (∼1.4 nm) confined in silica layers on NrGO (Pd/NrGO@SiO2) demonstrate a very high forward peak current density for formic acid oxidation (FAO) of 2.37 A mg-1, outperforming the Pd/C catalyst (0.30 A mg-1) and the Pd/rGO catalyst obtained by a conventional method (0.42 A mg-1). More importantly, our confined Pd catalysts show the highest stability of only 5% inconspicuous degradation of the initial mass activity after 1000 cycles, compared with Pd/C (almost 100% loss), Pd/rGO (61.5% loss) and Pd/NrGO (73.2% loss). These strategies in this work provide a new prospect for the design of excellent noble catalysts to overcome the challenges in the practical application of DFAFCs.

Ruthenium on phosphorous-modified alumina as an effective and stable catalyst for catalytic transfer hydrogenation of furfural

Supported ruthenium was used in the liquid phase catalytic transfer hydrogenation of furfural. To improve the stability of Ru against leaching, phosphorous was introduced on a Ru/Al₂O₃ based catalyst upon impregnation with ammonium hypophosphite followed by either reduction or calcination to study the effect of phosphorous on the physico-chemical properties of the active phase. Characterization using X-ray diffraction, solid state ³¹P nuclear magnetic resonance spectroscopy, X-ray absorption spectroscopy, temperature programmed reduction with H₂, infrared spectroscopy of pyridine adsorption from the liquid phase and transmission electron microscopy indicated that phosphorous induces a high dispersion of Ru, promotes Ru reducibility and is responsible for the formation of acid species of Brønsted character. As a result, the phosphorous-based catalyst obtained after reduction was more active for catalytic transfer hydrogenation of furfural and more stable against Ru leaching under these conditions than a benchmark Ru catalyst supported on activated carbon.

Phosphorous induces structural changes in Ru/Al₂O₃ that make it more active and more stable for liquid phase hydrogenation of furfural.

Highly Active and Durable Ultrasmall Pd Nanocatalyst Encapsulated in Ultrathin Silica Layers by Selective Deposition for Formic Acid Oxidation

The low performance of palladium (Pd) is a considerable challenge for direct formic acid fuel cells in practical applications. Herein, we develop a simple strategy to synthesize a highly active and durable Pd nanocatalyst encapsulated in ultrathin silica layers with vertically aligned nanochannels covered graphene oxides (Pd/rGO@pSiO₂) without blocking active sites by selective deposition. The Pd/rGO@pSiO₂ catalyst exhibits very high performance for a formic acid oxidation (FAO) reaction compared with the Pd/rGO without protective silica layers and commercial Pd/C catalysts. Pd/rGO@pSiO₂ shows an FAO activity 3.9 and 3.8 times better than those of Pd/rGO and Pd/C catalysts, respectively. The Pd/rGO@pSiO₂ catalysts are also almost 6-fold more stable than Pd/C and more than 3-fold more stable than Pd/rGO. The outstanding performance of our encapsulated Pd catalysts can be ascribed to the novel design of nanostructures by selective deposition fabricating ultrasmall Pd nanoparticles encapsulated in ultrathin silica layers with vertically aligned nanochannels, which not only avoid blocking the active sites but also facilitate the mass transfer in encapsulated catalysts. Our work indicates an important method to the rational design of high-performance catalysts for fuel cells in practical applications.

Cu5Pt Dodecahedra with Low-Pt Content: Facile Synthesis and Outstanding Formic Acid Electrooxidation

Tailoring composition and structure are significantly important to improve the utilization and optimize the performance of the precious Pt catalyst toward various reactions, which greatly relies on the feasible synthesis approach. Herein, we demonstrate that Cu-rich Cu₅Pt alloys with unique excavated dodecahedral frame-like structure (Cu₅Pt nanoframes) can be synthesized via simply adjusting the amounts of salt precursors and surfactants under hydrothermal conditions. It is established that the presence of hexamethylenetetramine and cetyltrimethylammonium bromide, as well as the selection of a proper Pt/Cu ratio are key for the acquisition of the target product. The immediate appeal of this material stems from frame-like architecture and ultralow Pt content involved, which can be used to greatly improve the utilization efficiency of Pt atoms. When benchmarked against commercial catalysts, the developed Cu₅Pt nanostructures display superior electrocatalytic performance toward formic acid oxidation, owing to unique electronic effect and ensemble effect. This work elucidates a promising methodology for the synthesis of Pt-based nanostructures while highlights the significance of composition and structure in electrocatalysis.