Cold plasma for preparation of Pd/C catalysts toward formic acid dehydrogenation: Insight into plasma working gas

Plasma synthesis of defect-rich flexible carbon cloth decorated with PtRu alloyed nanoclusters for highly efficient pH-universal electrocatalytic hydrogen evolution

Designing electrocatalysts with superior activity and stability to Pt/C for the highly efficient pH-universal electrochemical hydrogen evolution reaction (HER) still remains an urgent challenge. Herein, we report a facile plasma method for the preparation of defect-rich flexible carbon cloth decorated with ultralow-loading (0.1 wt%) PtRu alloyed nanoclusters (PtRu/CC-P) to resolve these problems. Remarkably, the developed PtRu/CC-P catalyst delivered a high mass activity of 3.77 A mg^-1 (η = 100 mV), almost 3.6 times higher than that of the benchmark HER electrocatalyst 20%Pt/C (1.05 A mg^-1). Meanwhile, it only required a low overpotential of 44 mV to achieve a current density of 10 mA cm^-2 in alkaline media. Systematic experimental and DFT calculation results revealed that the Pt-Ru bridge of PtRu alloyed nanoclusters in PtRu/CC-P can optimize the adsorption strength of HER intermediates at active sites, decrease the H₂O dissociation energy barrier, and consequently facilitate the HER kinetics. Inspiringly, when the PtRu content was increased to 1 wt%, PtRu/CC-P still exhibited a relatively low overpotential of 276 mV even at a high current density of 1000 mA cm^-2 and maintained excellent durability at a relatively high current density of 50-500 mA cm^-2 for more than 15 h in alkaline media. In addition, PtRu/CC-P also showed brilliant HER activity and stability in neutral and acidic media. This facile method provides a feasible route for the rational design of Pt-based alloyed catalysts toward industrial hydrogen production at all-pH values.

Resonant Power Supply for Plasma Cleaning Based on Fuzzy Logic Power Tracking

The coaxial cylindrical reactor with a rotary nozzle is proposed to be used as the plasma torch of the plasma cleaning machine. The phase-shifted full bridge series resonance circuit is used as the power circuit topology. Because the voltage source load resonance circuit technology is mature, the cycle and difficulty of research and development on this basis are relatively small, and the corresponding control strategy and algorithm are relatively easy to achieve. At the same time, the voltage source circuit is smaller than the current source circuit, in line with the development trend of plasma cleaning equipment. In this paper, based on the phase shift full bridge series resonant circuit, the control strategy is compared and analyzed. Considering the response speed, control precision and efficiency, a PSPWM-PFM (Phase Shift Pulse Width Modulation- Pulse Frequency Modulation) hybrid modulation control strategy is proposed, which makes the system not only have a fast response speed but can also construct a soft switch and has a high efficiency. A maximum power tracking algorithm based on a fuzzy PFM was proposed to solve the problem that the plasma power supply deviated from the resonant frequency point easily due to environmental perturbation, and thus deviated from the maximum power point.

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.