Ultrafine Pd nanoparticles on amine-functionalized carbon nanotubes for hydrogen production from formic acid

Synergistically driven PdCo alloy based on cross-linked carbon dots for efficient formic acid dehydrogenation

Modifying the electronic structure of precious metals by alloying with non-precious metals is a proven strategy for enhancing the performance of dehydrogenation catalysts. In this work, a PdCo alloy catalyst supported on N-doped carbon dots (NCDs) was synthesized using a straightforward hydrothermal and reduction process. This catalyst effectively promoted the dehydrogenation of formic acid without the need for any additives at 323 K. The confinement effect of NCDs facilitated the formation of uniformly dispersed PdCo alloy particles (average size of 2.7 nm). X-ray photoelectron spectroscopy analysis revealed that the addition of Co not only increases the electron density of Pd but also enhances the electronic support from the electron-rich N atoms in NCDs, thereby significantly improving catalytic activity. Through optimization of the Pd-to-Co molar ratio, it was determined that Pd9Co1/NCDs exhibited superior activity for formic acid dehydrogenation. The turnover frequency of the catalyst was 593 h-1 and the activation energy of the dehydrogenation process was 39.3 kJ·mol-1. This research established an experimental basis for designing noble metal-based catalysts with enhanced catalytic efficiency.

Unlocking Improved Formic Acid Dehydrogenation of Pd Nanoparticles Immobilized on Amine-Functionalized Yolk-Shell Silica

In this work, a series of mesoporous yolk-shell silica spheres (YS-x) with tunable yolk size and shell thickness were synthesized via the incubation method in water. Following amination and Pd loading treatment on YS-x, a series of catalysts Pd-YS-x-NH2 were obtained successfully and applied to formic acid (FA) dehydrogenation for hydrogen (H2) generation. The optimal catalyst Pd-YS-6-NH2, which has an appropriate yolk size and shell thickness, the largest specific surface area, and pore volume, as well as the smallest Pd nanoparticles (NPs), exhibits dehydrogenation performance far superior to that of other reference catalysts. It shows an extraordinary turnover frequency (TOF, 4508 h-1) and excellent stability at 60 °C with sodium formate (SF). After five testing cycles, it still maintained 100% FA conversion, and the decline in catalytic performance is almost negligible. The excellent catalytic performance of Pd-YS-6-NH2 is attributed to the optimal yolk-shell structure, the introduction of amine groups, and highly dispersed and ultrasmall Pd NPs (1.5 nm). This study provides methods for yolk-shell catalyst design and development for FA dehydrogenation.

Efficient hydrogen production from formic acid dehydrogenation over ultrasmall PdIr nanoparticles on amine-functionalized yolk-shell mesoporous silica

Developing heterogeneous catalysts with exceptional catalytic activity over formic acid (HCOOH, FA) dehydrogenation is imperative to employ FA as an effective hydrogen (H2) carrier. In this work, ultrasmall (1.4 nm) and well-dispersed PdIr nanoparticles (NPs) immobilized on amine-functionalized yolk-shell mesoporous silica nanospheres (YSMSNs) with radially oriented mesoporous channels have been synthesized by a co-reduction strategy. The optimized catalyst Pd4Ir1/YSMSNs-NH2 (Pd/Ir molar ratio = 4:1) exhibited a remarkable turnover frequency (TOF) of 5818 h-1 and remarkable stability at 50 °C with the addition of sodium formate (SF), resulting in complete FA conversion and H2 selectivity, exceeding most of the solid heterogeneous catalysts in previous reports under similar circumstances. Kinetic isotope effect (KIE) exploration indicates the cleavage of the CH bond is regarded as the rate-determining step (RDS) during the FA dehydrogenation process. Such excellent catalytic properties arise from the ultrafine and well-dispersed PdIr NPs supported on the nanosphere support YSMSNs-NH2, the electronic synergistic effect of PdIr alloy NPs, and the strong metal-support interaction (MSI) effect between the introduced PdIr NPs and YSMSNs-NH2 support. This work offers a new paradigm for exploiting the highly effective silica-supported Pd-based heterogeneous catalysts over the dehydrogenation of FA.

Carbon-coated silica supported palladium for hydrogen production from formic acid - Exploring the influence of strong metal support interaction

Hydrogen energy is one of the most promising energy carriers to solve the increasingly severe energy crisis. Formic acid decomposition (FAD) solves the storage and transportation problems of hydrogen gas since hydrogen can be produced from aqueous formic acid under mild conditions. To efficiently convert formic acid to hydrogen gas, chemical and structural modification of Pd nanoparticles or supports have been carried out, especially introducing the strong metal support interaction (SMSI). Herein, we synthesized core-shell structured SiO2@SC compounds as the supports to introduce SMIS to Pd/PdO nanoparticles. The relationship between FAD activity and SMSI is investigated. The SMSI between Pd/PdO nanoparticles and SiO2/SC is adjusted by altering the thickness of the carbon layer. The X-ray photoelectron spectroscopy shows that owing to the strong electron-attracting ability SiO2 core contributes to leading the Pd0 active site in an electron-deficient state. The thickness of the carbon layer controls the ratio of Pd0/PdO, which enhances the anti-poisoning ability of the catalyst. Owing to the electron-deficient state of Pd0 and optimal ratio of Pd0/PdO, the hydrogen desorption rate of FAD on Pd is enhanced, and the turn over frequency of Pd/SiO2@SC-1:3 catalyst reaches 1138 h-1, which is ten times higher than that of the pristine Pd/SC catalyst. These results are believed to guide the design and development of highly active Pd-based catalysts for hydrogen generation via FAD.

Hydrogen Evolution from Additive-Free Formic Acid Dehydrogenation Using Weakly Basic Resin-Supported Pd Catalyst

Hydrogen, as a noncarbon energy source, plays a significant role in future clean energy vectors. However, concerns about the safe storage and transportation of hydrogen gas limit its wide application. Featured with high H₂ volumetric density, nontoxicity, and nonflammability, formic acid (FA) is regarded as one of the most encouraging chemical hydrogen carriers. The search for heterogeneous catalysts with decent catalytic activity and stability for FA decomposition is one of the hottest research topics in this area. In this paper, three weakly basic resins with different functional groups, including D201 with -N⁺(CH₃)₃, D301 with -N(CH₃)₂, and D311 with -NH₂, were investigated as alternative catalyst supports for Pd catalysts. The prepared basic resin-supported Pd catalysts were evaluated for the FA dehydrogenation reaction under atmospheric pressure and temperatures ranging from 30 to 70 °C. The results showed that the catalytic activity of the three different resin-supported Pd catalysts follows the order of Pd/D201 > Pd/D301 > Pd/D311. Particularly, a high turnover frequency value of 547.6 h^-1 was achieved when employing Pd/D201 as the FA dehydrogenation reaction catalyst at 50 °C. The apparent activation energies for the three different Pd/resin catalysts were calculated, of which the Pd/D210 catalyst demonstrates the lowest activation energy of 42.9 kJ mol^-1. The reasons for the superior catalytic behavior, together with the reaction mechanism, were then investigated and illustrated.

Efficient and Controlled H2 Release from Sodium Formate

Sodium formate (SF) has been used for a long time as a technological additive for H2 release from the dehydrogenation of formic acid . Formic acid is often synthesized from...