Chromic hydroxide-decorated palladium nanoparticles confined by amine-functionalized mesoporous silica for rapid dehydrogenation of formic acid

Microenvironment Modulation of Single-Atom Ru in ZrSBA-15 for CO2 Hydrogenation to Formic Acid

The chemical microenvironment modulation of active sites holds promise for facilitating their catalytic performance. Herein, single-atom Ru anchored by ZrSBA-15 modified with diverse organic amine groups has been fabricated and enabled CO2 hydrogenation to produce formic acid (FA) under mild conditions. However, the reaction cannot be achieved without the modification of organic amines. The functional groups as the microenvironment around Ru active sites effectively regulated the activity, in which Ru encapsulated in ZrSBA-15 bearing -NH2 groups exhibited the highest activity, with turnover number (TON) and turnover frequency (TOF) values of 505 and 64 h-1, respectively. Both characterization and experimental results validated that the functional group manipulated the adsorption capacity of the reactant, the electronic state of Ru and hydrophilicity/hydrophobicity of the materials, and thus the catalytic performance.

Selective and controlled H2 generation upon additive-free HCOOH dehydrogenation over a Pd/NCS nanocatalyst

Although sodium formate is widely used as a conventional additive to enhance selective H2 evolution from HCOOH dehydrogenation, this leads to a waste of resources and an increase in the cost of H2 production. For this reason, N-doped carbon nanospheres with abundant graphitic C/N have been designed to enrich the electron cloud density of the Pd atom for improving its catalytic activity in H2 generation upon additive-free HCOOH dehydrogenation. Herein, we have synthesized N-doped carbon nanosphere-stabilized Pd nanoparticles (Pd/NCSs) as high-efficiency nano-catalysts, via fixation of Pd nanoparticles onto N-doped carbon nanospheres (NCSs), for selective and controlled H2 generation upon additive-free HCOOH dehydrogenation. Pd/NCS-800 (1640 h-1) provided a 12 times larger TOF than commercial Pd/C (134 h-1) in H2 generation upon additive-free HCOOH dehydrogenation. It seemed that graphitic N/C of NCS-800 enriched the electron cloud density of the Pd atom, which was favorable for the cleavage of C-H bonds in HCOOH dehydrogenation. In addition, the selective H2 evolution from additive-free HCOOH dehydrogenation over Pd/NCS-800 is successfully controlled by adjusting the pH.

Carbon bowl-confined subnanometric palladium-gold clusters for formic acid dehydrogenation and hexavalent chromium reduction

Formic acid (FA), a high-value product of CO₂ hydrogenation and biomass conversion, is considered a promising liquid organic hydrogen carrier for its high hydrogen content, easy accessibility, and relative stability. The development of an efficient heterogeneous catalyst toward FA dehydrogenation and Cr(VI) reduction by FA is needed to boost its sluggish kinetics but still remains a challenge. Herein, uniformly dispersed subnanometric PdAu alloy clusters (i.e., 0.9 nm) were successfully prepared and confined by amine-functionalized carbon bowls (ACB). By virtue of the tiny size and abundant active sites of PdAu clusters, the promotional effect of surface amine groups, and electronic interaction between subnanometric PdAu clusters and support, this as-prepared PdAu/ACB catalyst exhibits superior catalytic property for additive-free FA dehydrogenation (turnover frequency, 10597 h^-1 at 323 K) and Cr(VI) reduction (rate constant, 0.47 min^-1 at 298 K) under mild conditions, higher than most of the catalysts reported so far. This study offers insight into the design of efficient and durable catalysts for various catalytic applications in energy and environment.

A Recent Review of Primary Hydrogen Carriers, Hydrogen Production Methods, and Applications

Hydrogen is a promising energy carrier, especially for transportation, owing to its unique physical and chemical properties. Moreover, the combustion of hydrogen gas generates only pure water; thus, its wide utilization can positively affect human society to achieve global net zero CO2 emissions by 2050. This review summarizes the characteristics of the primary hydrogen carriers, such as water, methane, methanol, ammonia, and formic acid, and their corresponding hydrogen production methods. Additionally, state-of-the-art studies and hydrogen energy applications in recent years are also included in this review. In addition, in the conclusion section, we summarize the advantages and disadvantages of hydrogen carriers and hydrogen production techniques and suggest the challenging tasks for future research.