Accelerating hydrogen evolution rate and preventing metal hydroxide deposition in seawater electrolysis via addition of chelating agent EDTA-Na4

Large-scale hydrogen production via water electrolysis faces a freshwater shortage. Direct seawater electrolysis offers a solution but encounters new challenges. Herein, we report a feasible strategy to both prevent metal hydroxides deposition and boost the hydrogen evolution reaction by adding a chelating agent, EDTA-Na4, that chelates with Mg2+/Ca2+, thus inhibiting their deposition and gathering them near the cathode surface, resulting in breaking the ordered hydrogen bond networks of interfacial water and reducing the activation energy of water dissociation. Furthermore, hydrolysis of –COO− also promoted water dissociation to produce more active *H and *OH near the electrode surface that in turn serves as a diffusion medium for *OH, accelerating mass transfer and enabling seawater electrolysis to exhibit a stable performance, which operates continuously at 100 mA cm−2@2.20 V and 200 mA cm−2@2.58 V for 400 h in the symmetric electrolyzer and 500 mA cm−2@2.29 V for over 500 h in the asymmetric electrolyzer. This study provides a new perspective to address the issues of stable and scalable direct seawater electrolysis for practical green hydrogen production.