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.

Boron nitride nanosheets supported highly homogeneous bimetallic AuPd alloy nanoparticles catalyst for hydrogen production from formic acid

Formic acid (FA) has been recently regarded as a safe and stable source of hydrogen (H₂). Selective and efficient dehydrogenation of FA by an effective catalyst under mild conditions is still a challenge. So, different molar ratios of bimetallic Pd-Au alloy nanoparticles were effectively stabilized and uniformly distributed on boron nitride nanosheets (BNSSs) surface via the precipitation process. Obtained catalysts were employed in FA decomposition for H₂production. Pd-Au@BNNS containing 3% Au and 5% Pd (Au_.03Pd_.05@BNNS) exhibited high activity and 100% H₂selectivity for H₂production from FA at 50 °C. In order to optimize the reaction conditions, various factors including, time, temperature, solvent, base type, and amount of catalyst, were examined.

Controlled synthesis of Bi- and tri-nuclear Cu-oxo nanoclusters on metal-organic frameworks and the structure-reactivity correlations

Precisely tuning the nuclearity of supported metal nanoclusters is pivotal for designing more superior catalytic systems, but it remains practically challenging. By utilising the chemical and molecular specificity of UiO-66-NH2 (a Zr-based metal-organic framework), we report the controlled synthesis of supported bi- and trinuclear Cu-oxo nanoclusters on the Zr6O4 nodal centres of UiO-66-NH2. We revealed the interplay between the surface structures of the active sites, adsorption configurations, catalytic reactivities and associated reaction energetics of structurally related Cu-based 'single atoms' and bi- and trinuclear species over our model photocatalytic formic acid reforming reaction. This work will offer practical insight that fills the critical knowledge gap in the design and engineering of new-generation atomic and nanocluster catalysts. The precise control of the structure and surface sensitivities is important as it can effectively lead to more reactive and selective catalytic systems. The supported bi- and trinuclear Cu-oxo nanoclusters exhibit notably different catalytic properties compared with the mononuclear 'Cu1' analogue, which provides critical insight for the engineering of more superior catalytic systems.

Carbon-Doping as Efficient Strategy for Improving Photocatalytic Activity of Polysilicon Supported Pd in Hydrogen Evolution from Formic Acid

Interest in cost-effective materials pushes researchers to the inexpensive and abundant semiconductors to use photons' energy for generating electrons and holes required for photocatalytic transformations. At the same time, polysilicon is one of the economic semiconductors with a disadvantage of high bandgap which could be solved by carbon-doping. We employed this strategy to the synthesis of carbon-doped polysilicon by a new approach starting from citric acid and methyltrimethoxysilane. The nanocomposite obtained was utterly characterized, and compared with bare polysilicon; increased UV-Vis absorbance and shift to higher wavelengths were the most notable characteristics of the synthesized catalyst. The carbon-doped polysilicon was modified with Pd nanoparticles to obtain a new heterogeneous photocatalyst for the formic acid degradation. The decomposition of formic acid was photocatalyzed by the obtained nanocomposite with a hydrogen production turnover frequency of up to 690 h-1. Moreover, it was demonstrated that the catalyst is stable and recyclable.

Density functional study on formic acid decomposition on Pd(111) surface: a revisit and comparison with other density functional methods

The mechanism of formic acid decomposition on the Pd(111) surface has been investigated by several theoretical methods in previous studies, including PBE and PW91. These results indicated that the mechanism is different from different methods, and even by using the same method (i.e., PBE), the mechanism is also different. In this study, we have revisited the formic acid decomposition on Pd(111) surface by using another density functional RPBE and by including van der Waals interaction which is neglected in the previous studies. Our results showed that the formic acid is decomposed via O-H bond cleavage to form bi-HCOO^*, and the most favorable pathway is HCOOH^* → bi-HCOO^* + H^* → CO₂^* + 2H^*. The energy barrier is 0.55 eV at the rate-determining step. This conclusion is consistent with one of the PBE study. This demonstrated that computational methods have a great influence on the reaction mechanism, and care should be taken in selecting the appropriate computational methods.

AuPd bimetallic nanoparticles supported on reduced graphene oxide nanosheets as catalysts for hydrogen generation from formic acid under ambient temperature

Monometallic Au and Pd, and bimetallic Au_xPd_y (x/y mole ratio Au/Pd: 3 : 1, 1 : 1 and 1 : 3) catalysts supported on reduced graphene oxide (rGO) have been synthesised by the sol-immobilization method.