Zeolite Pb,Br,H,Cs,Na-Y was prepared by the reaction of Cs 49 Na 22 -Y with PbBr 2 in a mixed organic solvent, and the structure of a single crystal of it was determined crystallographically. About 26% of its supercages hold a tetrahedral PbBr 42− ion at their centers. Each is surrounded by six Cs + ions, each of which bridges between the two Br − ions on each edge of the PbBr 4 2− tetrahedron. Each of these four Br − ions also bonds to a Na + ion near the center of a 6-ring. The result is a Na 4 Cs 6 PbBr 4 8+ quantum dot (QD) of symmetry 4̅ 3m (T d ). The supercage in this zeolite (Si/Al = 1.69) has an average charge of 8.9−, which nearly balances the 8+ charge of this QD. Water molecules in 12-rings bridge (Cs + −H 2 O−Cs + ) between QDs in adjacent supercages to form domains of tetrahedrally arranged QDs. Both these QDs and these domains are seen directly by electron microscopy. These QDs, when excited by UV radiation, luminesce sharply at 528 nm (green, FWHM = 17.8 nm). Pb,Br,H,Cs,Na-Y and its luminescence are entirely stable in the atmosphere; the bridging water molecules enhance the luminescence and provide that stability. Structure refinement was done in the space group Fd3̅ m (a = 24.889(4) Å) with the 886 unique reflections for which F o > 3σ(F o ) to the final error index R 1 = 0.077. Its composition was confirmed by energy dispersive X-ray analysis.

The synergistic effect in multi‐metal electrocatalysts has gained attention as an efficient strategy for enhancing intrinsic electrocatalytic activities. In this study, a facile electrodeposition technique is used to synthesize a multi‐metal high entropy catalyst (HEC) for efficient electrocatalytic hydrogen production. To boost the synergistic effect between noble metals and transition metals, the Pt ratio is controlled in a multi‐metal electrocatalyst system. The prepared Pt‐involved HEC (Pt‐HEC) exhibits a bamboo‐like morphology with uniformly distributed elements. The 2.5 mM Pt‐HEC has outstanding electrocatalytic activity toward hydrogen evolution reaction (HER) among other Pt‐HECs, with a low overpotential of 70 mV and a Tafel slope value of 47 mV dec−1. Additionally, the Pt mass activity of the 2.5 mM Pt‐HEC is 5.6 times higher than commercial Pt/C electrocatalyst owing to the improved synergistic effect with an optimized Pt ratio. According to the electrochemical impedance spectroscopy (EIS) analysis, the proton‐coupled electron transfer (PCET) process occurs more quickly in the 2.5 mM Pt‐HEC electrocatalyst, confirming its smaller charge transfer resistance properties compared to those of the 5 and 1 mM Pt‐HEC. Therefore, HEC systems can be extensively encouraged as a platform for improving synergistic effects and enhancing electrocatalytic activities for a highly efficient HER electrocatalyst.