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Abstract The commercialization of zinc metal batteries (ZMBs) for large‐scale energy storage is hindered by challenges such as dendrite formation, the hydrogen evolution reaction (HER), and passivation/corrosion, which lead to poor stability of zinc metal anodes. HER is a primary contributor to this instability, and despite efforts to enhance ZMB cyclability, a significant knowledge gap remains regarding the origin of HER in these systems. Prior works, based primarily on theoretical calculations with minimal experimental support, suggest that HER originates from Zn²⁺‐solvated water. For the first time, by employing scanning electrochemical microscopy (SECM), and electrochemical mass spectrometry (ECMS), in real‐time the inherently intertwined nature of Zn electrodeposition and H₂ liberation is revealed, both exhibiting the same onset potential in voltammetry. The findings show that water molecules surrounding Zn²⁺ ions undergo reduction simultaneously during Zn²⁺ deposition. Additionally, ECMS conducted under chronopotentiometric/galvanostatic conditions at battery‐relevant current densities elucidates why elevated electrolyte concentrations enhance the prolonged cyclability of ZMBs. Understanding the origin of HER opens avenues for developing high‐performance, reliable aqueous ZMBs, addressing key challenges in their commercialization and advancing their technological capabilities. 

The NIS synthetase family of enzymes responsible for the biosynthesis of siderophores is increasingly associated with bacterial virulence. Proteins in this class represent outstanding potential drug targets, assuming that basic biochemical and structural characterizations can be completed. Towards this goal, we have mated an improved synthesis of the non-commercial amino acid N-hydroxy-N-succinylcadaverine (HSC, 6) with an isothermal titration calorimetry (ITC) assay that profiles the iterative stages of HSC trimerization and macrocyclization by NIS synthetase DesD from Streptomyces coelicolor. HSC synthesis begins with multigram-scale Gabrielle and tert-butyl N-(benzyloxy)carbamate alkylations of 1-bromo-5-chloropentane following prior literature, but the end-game reported herein has two advantages for greater material throughput: (1) hydrogenolysis of benzyl ether and Cbz blocking groups is best accomplished with Pearlman’s catalyst at 40 psi of H2 and (2) purification of neutral (zwitterionic) HSC is effected by simple flash chromatography over silica gel in MeOH. HSC is subsequently shown to be a substrate for NIS synthetase DesD, which catalyzes three successive amide bond syntheses via adenyl monophosphate ester intermediates. We quantify and present the iterative and overall enzyme kinetic constants associated with formation of the cyclotrimeric siderophore desferrioxamine E (dfoE, 1).