Metal nanoparticles, clusters, and single atoms exhibit remarkable variations in catalytic performance due to their different electronic and atomic structures. To explore the size-dependent effects on acetylene hydrochlorination, a series of Ru catalysts (including single atoms (Ru SAC CS), clusters (Ru ACs CS), and nanoparticles (Ru NPs CS) catalysts) were accurately synthesized by a defect-engineering strategy. Ru SAC CS demonstrated the optimal catalytic performance. The structural–activity relationship between the catalyst’s initial activity and charge, Ru–Ru coordination number and the oxidation state of Ru sites offer insights into how the structure of Ru active sites affects acetylene hydrochlorination at the atomic scale. Density functional theory (DFT) simulations reveal that the energy barrier for the rate-determine-step (*Cl approaching the *CH₂=CH intermediate to form *C₂H₃Cl) for Ru SAC CS is significantly lower, facilitating barrier overcoming and enhancing vinyl chloride formation. Furthermore, Ru SAC CS displays suitable adsorption energies for C₂H₂ and C₂H₃Cl, which is conducive to prevent coke deposition and enhance the catalytic stability. This research demonstrates the efficiency of Ru single-atom catalysts for acetylene hydrochlorination and offers new perspectives on the precise construction and catalytic mechanism of sub-nanometer catalysts.

The structural and operation parameters of the electrolyzer play important roles in the efficiency of alkaline water electrolysis. In this article, a three-dimensional numerical model coupled with the electric field and the Euler-Eulerian k-ε turbulence flow field was first established to simulate accurately the performance of alkaline electrolyzers, based on a compact assembly structure of the industrial alkaline water electrolyzers, especially at current densities higher than 5000 A·m^–2. The simulation results are compared with the experimental data to verify the accuracy of the model. Suitable operating conditions for concentration, flow rate and the optimal design method of the flow channel structure are obtained from the feedback of the electric and flow fields characteristics inside the electrolyzers. Properly increasing the electrolyte concentration and flow rate facilitates the reduction of cell voltage. The optimum concentration and flow rate of potassium hydroxide aqueous solution are evaluated to be 6.0–8.0 mol·L^–1 and 30.0–45.0 mL·min^–1, respectively. With the increase of the gap between electrode and membrane, the ohmic overpotential increases significantly. The triangular arrangement of conductive columns on the bipolar plate and the increase of the channel height are beneficial to improve the distribution uniformity of the fluid, while the channel height and the arrangement of the conductive columns have little effect on the voltage. Appropriately increasing the spacing between the conductive columns facilitates to reduce the voltage. Multiple outlets and inlets structure is conducive to produce a more uniform fluid distribution. The channel height has little effect on the multiple outlets and inlets electrolyzer. The multiple outlets and inlets electrolyzer G-2.5-T-0-5-3 with wide spacing of conductive columns combined with high flow rate not only can reduce the cell voltage, but also enhance the normal flow rate of the electrolyte on the electrode surface, allowing the best performance of the electrolyzer. This work provides useful guidance on the scale-up design and optimization of highly efficient electrolyzer for alkaline water electrolysis.