Tuning the alloy degree for Pd-M/Al2O3 (M=Co/ Ni /Cu) bimetallic catalysts to enhance the activity and selectivity of dodecahydro-N-ethylcarbazole dehydrogenation

Hydrogen is a promising candidate to substitute the fossil fuels. However, the efficient hydrogen storage technologies restrict the commercial applications. Developing new catalysts with high activity and selectivity is important for the dehydrogenation reaction in N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NECZ/12H-NECZ) hydrogen storage system. In this work, a series of Pd-M/Al₂O₃ (M = Co, Ni and Cu) bimetallic catalysts are synthesized successfully and show good performance in the dehydrogenation reaction of 12H-NECZ than the commercial Pd/Al₂O₃ catalyst. The Pd₁Co₁/Al₂O₃ catalyst (Practical Pd content = 2.4136 wt%) showed the highest catalytic performance with 95.34% H₂ release amount, TOF of 230.5 min⁻¹ and 85.4% selectivity of NECZ. Combined with the characterization analysis, it can be proposed that the dehydrogenation performance of 12H-NECZ is dependent on the alloy phases, reasonable electronic structures and nanoparticle size of catalysts. The fine-tuned alloy degree and appropriate nanoparticle size of Pd₁Co₁/Al₂O₃ bring the 17.7% increase of H₂ release amount and 99.5% increase of NECZ selectivity than those of Pd/Al₂O₃. For the bimetallic catalysts, the enhancement of selectivity of NECZ is mainly from the increase of the kinetic constant of rate-limiting step.     

Enhancing selectivity and reducing cost for dehydrogenation of dodecahydro-N-ethylcarbazole by supporting platinum on titanium dioxide

N-ethylcarbazole/dodecahydro-N-ethylcarbazole (NECZ/12H-NECZ) was a promising system for hydrogen storage applications. 1.0 wt% Pt/TiO₂ was regarded as the optimal loading in Pt/TiO₂ catalyst applied in the 12H-NECZ dehydrogenation reaction. The hydrogen release amount, selectivity to NECZ and TOF of 12H-NECZ dehydrogenation are 5.75 wt %, 98% and 229.73 min⁻¹ at 453 K. Compared with the commercial 5.0 wt% Pd and Pt-based catalysts, it exhibited very high activity, selectivity and stability for 12H-NECZ dehydrogenation with low Pt loading. Combined with the XRD, XPS, HRTEM, TPR analysis, it was indicated that the enhanced catalytic performance was due to the SMSI (strong metal-supporting interaction) between Pt and TiO₂ support, which accelerated the rate-limiting step and enhanced the whole dehydrogenation reaction. This work may be beneficial for the commercial application of Pt/TiO₂ catalysts in the Liquid Organic Hydrogen Carrier (LOHC) system.     

Boosting the dehydrogenation efficiency of dodecahydro-N-ethylcarbazole by assembling Pt nanoparticles on the single-layer Ti3C2Tx MXene

As the candidates for large-scale hydrogen storage, liquid organic hydrogen carriers (LOHCs) exhibit evident advantages in hydrogen storage density and convenience of storage and transportation. Among them, NECZ (N-ethylcarbazole)/12H-NECZ (dodecahydro-N-ethylcarbazole) is considered as a typical system with the lower hydrogenation/dehydrogenation temperature. However, the low dehydrogenation efficiency restrict its commercial applications. In this work, the single-layer Ti₃C₂T_x MXene was employed as the support to load the Pt nanoparticles for the 12H-NECZ dehydrogenation reaction. The effect of transition metals, loading amounts and morphologies of catalysts were analyzed. It was found that the 3 wt% Pt/S–Ti₃C₂T_x catalyst exhibited the best catalytic performance with 100% conversion, 91.55% selectivity of NECZ and 5.62 wt% hydrogen release amount at 453 K, 101.325 kPa for 7 h. The product distributions and kinetics analysis suggested that the elementary reaction from 4H-NECZ to NECZ was the rate-limiting step. The selectivity of NECZ is sensitive to the dehydrogenation temperature. Combined with the XRD, SEM, HRTEM, XPS, BET and FT-IR results, it could be indicated that the special two-dimension structure of S–Ti₃C₂T_x and electronic effect between Pt and S–Ti₃C₂T_x enhanced the dehydrogenation efficiency of 12H-NECZ. The measurements of cyclic dehydrogenation indicated that the Pt/S–Ti₃C₂T_x catalyst exhibited good stability after 42 h. This work brought a new strategy for the design of efficient catalysts using two-dimensional materials in the applications of the liquid organic storage hydrogen technology.     

A experimental study on the dehydrogenation performance of dodecahydro-N-ethylcarbazole on M/TiO2 catalysts

Liquid organic hydrogen carrier (LOHC) is considered as a promising candidate for large-scale hydrogen storage. In this work, we found that Pt/TiO₂ catalysts exhibited better catalytic activity and selectivity compared to Pd/TiO₂ and commercial Pd/Al₂O₃ catalysts in the dehydrogenation of dodecahydro-N-ethylcarbazole (12H-NECZ) at 453 K. The catalytic activity of the noble metal catalysts followed the trend of Pt/TiO₂ > Pd/TiO₂ > Rh/TiO₂ > Au/TiO₂ > Ru/TiO₂. Compared with the commercial Pd/Al₂O₃, Pt/TiO₂ greatly improved the selectivity and conversion rate, the reaction time was also shortened. In addition, kinetics calculation was carried out to obtain fundamental reaction parameters. It was found that the third step of 4H-NECZ dehydrogenation to NECZ was the rate-limiting step of the entire dehydrogenation reaction for all catalysts.     

Nickel-palladium nanoparticle catalyzed hydrogen generation from hydrous hydrazine for chemical hydrogen storage

In this study, we report Ni-Pd bimetallic nanoparticle catalysts (nanocatalyst) (Ni_1-xPd_x) synthesized by alloying Ni and Pd with varying Pd contents, which exhibit appreciably high H₂ selectivity (>80% at x = 0.40) from the decomposition of hydrous hydrazine at mild reaction condition with Ni_0.60Pd_0.40 nanocatalyst, whereas the corresponding monometallic counterparts are either inactive (Pd nanoparticles) or poorly active (Ni nanoparticles exhibit 33% H₂ selectivity). In addition to powder X-ray diffraction (XRD), X-ray photoelectron spectra (XPS) analysis and electron microscopy (TEM/SEM), the structural and electronic characteristics of Ni-Pd nanocatalysts were investigated and established using extended X-ray absorption fine structure (EXAFS) analysis. Unlike the high activity of Ni-Pd nanocatalysts, Pd-M (M = Fe, Co and Cu) bimetallic nanocatalysts exhibit poor catalytic activity. These results imply that alloy composition of Ni-Pd nanocatalysts is critical, where the co-existence of both the metals on the catalyst active surface and the formation of inter-metallic Ni-Pd bond results in high catalytic performance for the decomposition of hydrous hydrazine to hydrogen.     

PdCoNi nanoparticles supported on nitrogen-doped porous carbon nanosheets for room temperature dehydrogenation of formic acid

The development of cost-effective heterogeneous catalysts for the dehydrogenation of formic acid (FA) is the key challenge for the commercialization of FA as a hydrogen-storage medium. Herein, PdCoNi nanoparticles (NPs) with different element ratios supported on N-doped carbon nanosheets (N-CN) were designed, which exhibit excellent catalytic dehydrogenation performance for FA. Compared with PdCoNi NPs loaded on the carbon nanosheets (CN), the introduction of pyrrolic N to CN induces the formation of ultrafine, monodispersed and amorphous Pd_0.6Co_0.2Ni_0.2 NPs with a size of 1.60 nm, which significantly increases the number of active sites and the instant contact between FA and catalysts. The as-prepared Pd_0.6Co_0.2Ni_0.2/N-CN catalyst shows more than 99% conversion and 100% H₂ selectivity at room temperature, with a record-high initial turnover frequency (TOF_initial) of 1249.0 h⁻¹ among non-noble containing Pd-based catalysts, which demonstrates the high potential of Pd_0.6Co_0.2Ni_0.2/N-CN as a practical catalyst for the hydrogen generation from FA.     

In situ facile synthesis of bimetallic CoNi catalyst supported on graphene for hydrolytic dehydrogenation of amine borane

Well dispersed magnetically recyclable bimetallic Co_xNi_1−x (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9, 1) nanoparticles (NPs) supported on graphene have been synthesized via a facile in situ one-step procedure, using the mixture of sodium borohydride (NaBH₄) and methylamine borane (MeAB) as the reducing agent under ambient condition. These NPs were composition dependent for catalytic hydrolysis of amine boranes. Among all the CoNi/graphene catalysts tested, the Co_0.9Ni_0.1/graphene NPs exhibit the highest catalytic activity toward hydrolysis of AB with the turnover frequency (TOF) value of 16.4 (mol H₂ min⁻¹ (mol catalyst)⁻¹), being higher than that of most reported non-noble metal-based NPs, and even many noble metal-based NPs. Moreover, the activation energy (E_a) value is 13.49 kJ/mol, which is the second lowest value ever reported for catalytic hydrolytic dehydrogenation of ammonia borane, indicating the superior catalytic performance of the as-synthesized Co_0.9Ni_0.1/graphene catalysts. Additionally, Compared with other reducing agents, such as NaBH₄, AB, MeAB, and the mixture of NaBH₄ and AB, the as-synthesized Co_0.9Ni_0.1/graphene catalysts reduced by the mixture of NaBH₄ and MeAB exert the highest catalytic activity. The Co_0.9Ni_0.1 NPs supported on graphene exhibit higher catalytic activity than catalysts with other conventional supports, such as SiO₂, carbon black, and γ-Al₂O₃. Furthermore, the as-synthesized Co_0.9Ni_0.1/graphene NPs show good recyclability and magnetically reusability for the hydrolytic dehydrogenation of amine boranes, which make the practical reusing application of the catalysts more convenient.     

Graphene supported Pt–Ni bimetallic nanoparticles for efficient hydrogen generation from KBH4/NH3BH3 hydrolysis

Developing highly efficient and stable supported bimetallic nanoparticles catalysts via a facile strategy is one of the most admirable methods for sustainable hydrogen production from borohydride hydrolysis. Herein, we developed a facile technology for rapidly and straightforwardly manufacturing Pt–Ni bimetallic nanoparticles (BNPs) supported by partially reduced graphene oxide (prGO) with excellent catalytic activity and outstanding durability for hydrogen production from KBH₄ and NH₃BH₃ alkaline solution. The uniformly dispersed Pt₄₀–Ni₆₀ BNPs with a statistical size of around 2.6 nm exhibited a surprising catalytic activity of 23,460 mol-H₂·h^?1·mol-Pt^?1 at 308 K, moreover, whose activity was high up to 80% of the first time even after 30 runs, demonstrating an outstanding stability. The apparent activation energy for dehydrogenation of KBH₄ and NH₃BH₃ were respectively about 27.8 and 33.6 kJ/mol for the prepared Pt₄₀–Ni₆₀/prGO catalyst. The extraordinary catalytic activity of the Pt₄₀–Ni₆₀/prGO catalyst owing to the strong charge transfer effect between Pt–Ni BNPs and graphene.     

Design the PdCu/Ni2P electrocatalyst with high efficiency for ethanol oxidation reaction in alkaline media

To facilitate the electrocatalytic behavior of Direct Ethanol Fuel Cells (DEFCs), a sequence of bimetallic Pd_xCu_y/Ni₂P-C catalysts are synthesized via the microwave-assisted ethylene glycol reduction method. The results indicate that our designed Pd₂Cu/Ni₂P-C(1:1) catalyst owns high activity (3974.08 mA mg^?1_Pd), 8.3 times higher than the commercial Pd/C. The durability and the CO tolerance of the corresponding catalysts are also investigated by chronoamperometry (CA) and CO stripping measurements, implying Pd₂Cu/Ni₂P-C(1:1) shows good durability and the anti-CO poisoning ability for EOR in alkaline media. The electrochemical impedance spectra (EIS) analysis reveals lower charge transfer resistance for Pd₂Cu/Ni₂P-C(1:1). Combined with the results of XRD, HRTEM, XPS and electrochemical measurements, we found that the good electrocatalytic activity, CO tolerance and long-term durability of Pd₂Cu/Ni₂P-C(1:1) may be provided by the electronic and strain effect among Pd, Cu and Ni₂P, which will bring the downshift in the d-band center of catalysts and the weakened adsorption of intermediates.     

Carbon-supported Ni3B nanoparticles as catalysts for hydrogen generation from hydrolysis of ammonia borane

We report the preparation of Ni₃B and carbon-supported Ni₃B (denoted as Ni₃B/C) nanoparticles, and their catalytic performance for hydrogen generation from hydrolytic dehydrogenation of ammonia borane (NH₃BH₃, AB). Ni₃B and Ni₃B/C were prepared via a chemical reduction and crystallization in tetraethylene glycol solution. The obtained Ni₃B catalysts are in well-defined crystalline state and Ni₃B/C catalysts have a high dispersion in the carbon. The hydrogen generation measurement shows that the carbon-supported Ni₃B presents enhanced catalyst activity during hydrolytic dehydrogenation of AB. Among the as-prepared Ni₃B/C catalysts, Ni₃B/C with 34.25 wt% Ni₃B loading displays the best catalytic activity, delivering a high hydrogen release rate of 1168 mL min⁻¹ g⁻¹ and the lower activation energy of 46.27 kJ mol⁻¹. The kinetic results show that the hydrolysis is a first-order reaction in catalyst concentration, while it is a zero-order in AB concentration. Furthermore, the Ni₃B/C is a recyclable catalyst under mild reaction conditions, indicating that the carbon-supported Ni₃B is a promising catalyst for AB hydrolytic dehydrogenation.     

Nitrogen-phosphorus co-functionalized reduced graphene oxide supported NiCoPd-CeOx nanoparticles as a highly efficient and stable catalyst for formic acid dehydrogenation

Formic acid (HCOOH, FA), a common liquid hydrogen storage material, has attracted tremendous research interest. However, the development of efficient, low-cost and high-stable heterogeneous catalyst for selective dehydrogenation of FA remains a major challenge. In this paper, a simple co-reduction method is proposed to synthesize nitrogen-phosphorus co-functionalized rGO (NPG) supported ultrafine NiCoPd-CeO_x nanoparticles (NPs) with a mean size of 1.2 nm. Remarkably, the as-prepared Ni_0.2Co_0.2Pd_0.6-CeO_x/NPG shows outstanding catalytic activity for FA dehydrogenation, affording a high TOF value of 6506.8 mol H₂ mol Pd^?1 h^?1 at 303 K and a low activation energy of 17.7 kJ mol^?1, which is better than most of the reported heterogeneous catalysts, and can be ascribed to the combined effect of well-dispersed ultrafine NiCoPd-CeO_x NPs, modified Pd electronic structure, and abundant active sites. The reaction mechanism of dehydrogenation of FA is also discussed. Furthermore, the optimized Ni_0.2Co_0.2Pd_0.6-CeO_x/NPG shows excellent stability over 10^th run with 100% conversion and 100% H₂ selectivity, which may provide more possibilities for practical application of FA system on fuel cells.     

Ammonia decomposition over SiO2-supported Ni–Co bimetallic catalyst for COx-free hydrogen generation

NH₃ decomposition over non-noble catalyst to generate CO_x-free H₂ has attracted great attention in recent years. In this work, fumed SiO₂-supported Ni, Co and Ni–Co bimetallic catalysts are synthesized by using a co-impregnation method and evaluated for NH₃ decomposition, which shows that the bimetallic catalysts exhibit better catalytic activity than the monometallic ones. This enhanced activity observed on bimetallic catalyst can be largely attributed to the more appropriate catalyst metal-N binding energy resulting from the synergistic effect between Ni and Co in the formed Ni–Co alloy. Among the synthesized catalysts, Ni₅Co₅/SiO₂ synthesized with the Ni/Co molar ratio of 5:5 achieves 76.8% NH₃ conversion under a GHSV of 30,000 mL h⁻¹ g⁻¹_cat at 550 °C and shows the best catalytic activity, which can be further improved by doping with K (78.1% NH₃ conversion at 30,000 mL h⁻¹ g⁻¹_cat), and the obtained Ni₅Co₅/SiO₂–K also shows excellent catalytic stability.     

Wet-impregnated bimetallic Pd-Ni catalysts with enhanced activity for dehydrogenation of perhydro-N-propylcarbazole

Palladium/platinum-based catalysts are widely used in the dehydrogenation process of Liquid Organic Hydrogen Carriers (LOHCs). The cost of noble metal has become a main drawback for LOHCs large-scale application. Partial replacement of Pd/Pt by other transition metals can be an effective solution. In this paper, we synthesize the bimetallic Pd–Ni catalyst by incipient wet impregnation and the catalytic dehydrogenation performance of perhydro-N-propylcarbazole (12H-NPCZ) as a LOHC candidate. Ni and Pd were impregnated on mesoporous alumina to obtain both monometallic and bimetallic catalysts, i.e. Pd/Al₂O₃, Ni/Al₂O₃ and Pd–Ni/Al₂O₃ (Pd:Ni = 1:1) with total metal loading of 5 wt%, respectively. The above catalysts were characterized by N₂-adsorption/desorption, H₂-temperature programmed reduction, X-Ray diffraction, X-Ray photoelectron spectroscopy, Inductively coupled plasma - optical emission spectrometer, CO pulse adsorption and Transmission electron microscopy. The catalytic dehydrogenation results indicated that the bimetallic Pd–Ni/Al₂O₃ showed best catalytic activity, followed by Pd/Al₂O₃, commercial Pd/Al₂O₃ and Ni/Al₂O₃. Notably, the catalytic activity of bimetallic was well maintained after 5 cycles at 200 °C with no degradation, indicating this bimetallic catalyst has potential prospect for large-scale application.     

Engineering hierarchical NiFe-layered double hydroxides derived phosphosulfide for high-efficiency hydrogen evolving electrocatalysis

Exploring robust, highly efficient, and cost-effective non-noble metal electrocatalysts for replacing Pt in hydrogen evolution reaction (HER) is of great significance. In this study, we skillfully synthesized binary transition-metal (i.e., nickel and iron) phosphosulfides on nickel foam (NiFeSP/NF) via a sulfuration/phosphorization treatment of bimetallic layered double hydroxides (LDH). Taking the advantage of the presence of active heterointerfaces among Ni₂P, Ni₃S₂, and FeS₂, the NiFeSP/NF catalyst, which was advantageous of the highly exposed active sites, exhibited an extraordinary catalytic activity in HER—an overpotential of 70 mV at a current density of 10 mA cm⁻² and a Tafel slope of 69 mV dec⁻¹, outperforming most of the existing counterparts. Moreover, NiFeSP/NF catalysts demonstrated favorable long-term catalytic stability for 10 h. We contributed this superior catalytic activity to the characteristic attributes of NiFeSP/NF, which could be stemmed from its exquisite catalyst design: (i) the co-occurrence of highly HER-favored crystalline Ni₂P, Ni₃S₂, and FeS₂ in bimetallic phosphosulfides and (ii) the existence of multi-functional phase interfaces among Ni₂P, Ni₃S₂, and FeS₂ in the NiFeSP/NF hierarchical structure. The present study exemplified an effective strategy for designing HER-favored bimetallic phosphosulfides and provided the scientific base for the insight into the catalytic nature of multi-metallic phosphosulfides.     

Hydrogen production from oxidative steam reforming of methanol: Effect of the Cu and Ni impregnation on ZrO2 and their molecular simulation studies

Cu and Ni were supported on ZrO₂ by co-impregnation and sequential impregnation methods, and tested in the oxidative steam reforming of methanol (OSRM) reaction for H₂ production as a function of temperature. Surface area of the catalysts showed differences as a function of the order in which the metals were added to zirconia. Among them, the Cu/ZrO₂ catalyst had the lowest surface area. XRD patterns of the bimetallic catalysts did not show diffraction peaks of the Cu, Ni or bimetallic Cu–Ni alloys. In addition, TPR profiles of the bimetallic catalysts had the lowest reduction temperature compared with the monometallic samples. The reactivity of the catalysts in the range of 250–350 °C showed that the bimetallic samples prepared by successive impregnation had highest catalytic activity among all the catalysts studied. These results were also confirmed by theoretical calculations. The reactivity of the monometallic and bimetallic structures obtained by molecular simulation followed the next order: Ni_shellCu_core/ZrO₂ ≅ Cu_shellNi_core/ZrO₂ > Ni/Cu/ZrO₂ > Cu/Ni/ZrO₂ > Cu–Ni/ZrO₂ > Cu/ZrO₂ > Ni/ZrO₂. These findings agree with the experimental results, indicating that the bimetallic catalysts prepared by successive impregnation show a higher reactivity than the Cu–Ni system obtained by co-impregnation. In addition, the selectivity for H₂ production was higher on these catalysts. This result could be associated also to the presence of the bimetallic Cu–Ni and core–shell Ni/Cu nanoparticles on the catalysts, as was evidenced by TEM–EDX analysis, suggesting that the OSRM reaction may be a structure–sensitive reaction.     

Hydrogen generation from formic acid decomposition at room temperature using a NiAuPd alloy nanocatalyst

Formic acid has been widely regarded as a safe and sustainable hydrogen storage material. Despite tremendous efforts, developing low-noble-metal-loading material with high activity for the dehydrogenation of formic acid remains a great challenge. Here, carbon supported highly homogeneous trimetallic NiAuPd alloy nanoparticles are prepared and employed as catalyst for the selective dehydrogenation of formic acid. Unexpectedly, at Ni molar contents as high as 40%, the resultant Ni_0.40Au_0.15Pd_0.45/C exhibits high activity and 100% hydrogen selectivity for hydrogen generation from formic acid aqueous solution without any additives even at 298 K. Such a low-noble-metal-loading catalyst with high activity may greatly encourage the practical application of formic acid as a hydrogen storage material.     

Bimetallic nickel-based nanocatalysts for hydrogen generation from aqueous hydrazine borane: Investigation of iron,cobalt and palladium as the second metal

Herein we present and discuss the catalytic activity results of nickel-based bimetallic nanoparticles towards the two-step dehydrogenation of hydrazine borane N₂H₄BH₃. Cobalt, iron and palladium were chosen as the second metal, and a series of Ni_1−xM_x nanocatalysts were prepared by surfactant-aided co-reduction method. The challenge was to find a nanocatalyst that is active in the decomposition of the N₂H₄ moiety of hydrazine borane. Of the 14 Ni_1−xM_x combinations, the best results were achieved with Ni_0.7Fe_0.3 and Ni_0.7Pd_0.3. At 50 °C, 3.9 and 4.3 mol H₂ + N₂ per mole of N₂H₄BH₃ were measured, indicating an activity in the decomposition of the N₂H₄ moiety. Then, both nanocatalysts were characterized by XRD, SEM, EDX, TEM, SAED and XPS. Finally, the differences in catalytic activity were discussed in terms of electronic and geometric effects.     

High active pd@mil-101 catalyst for dehydrogenation of liquid organic hydrogen carrier

Highly dispersed Pd nanoparticles immobilized in MIL-101 (Pd@MIL-101) were prepared and used for the catalytic dehydrogenation of Liquid organic hydrogen carriers (LOHC). The as-synthesized catalysts were characterized and it was found that 3 wt% of Pd@MIL-101 embodied smaller and highly dispersed Pd NPs. The catalytic activities of as-synthesized catalysts were investigated by the dehydrogenation of a representative LOHC compound, perhydro-N-propylcarbazole (12H-NPCZ). The results indicated that 3 wt% Pd@MIL-101 catalyst exhibited good catalytic activity and good reusability for the dehydrogenation of 12H-NPCZ, which is superior to that of commercial 5 wt% Pd/Al₂O₃ catalyst. This study demonstrates that Pd@MIL-101 is a promising dehydrogenation catalyst for the application of LOHC technology.     

Hydrogen production from additive-free formic acid over highly active metal organic frameworks-supported palladium-based catalysts

The metal organic frameworks (MOFs) supported Pd catalysts for H₂ generation from formic acid (FA) were synthesized in this work, via a facile excessive impregnation-low temperature reduction approach. Among the synthetic catalysts, 10% Pd/MOF-Cr (18) displayed a remarkable performance for catalyzing FA dehydrogenation in additive-free aqueous solution, and the corresponding TOF_mid achieved 537.8 h^?1 at 323 K. Furthermore, the bimetallic Ni–Pd alloy catalysts were prepared by the introduction of Ni in the subsequent work. Fortunately, 10% Ni_0.4Pd_0.6/MOF-Cr was found to be a highly active and fairly durable catalyst, exhibiting a TOF_mid as high as 737.9 h^?1 at 323 K with almost 100% X_FA (final) and S_H2, and remained 94% of its original activity in the third cyclic catalysis. Meanwhile, Ni was discovered to be indispensable in increasing the electron density of Pd, downsizing the immobilized metal particles and inhibiting the agglomeration of the loaded nanoparticles.