Urea-mediated self-assembly of Ni foam supported Ni-BTC nanoflower arrays as superior cathode catalysts for high-performance aluminum/seawater batteries

The hydrogen evolution reaction (HER) largely determines the performance of Al/seawater batteries, but reported conventional HER catalysts possess low intrinsic activity in the seawater environment, even for the expensive and scarce Pt-based ones. For the first time, a NF-supported Ni-BTC nanoflower array (NF@Ni-BTC NFA) has been synthesized via urea-mediated self-assembly, whereby the urea in situ generates NH 3 to serve as a modulator to both coordinate with Ni 2+ and deprotonate BTC. This 3-D nanostructure exhibits superior HER activity than the NF-supported nanosheet array obtained without urea and even commercial Pt/C in the KOH-added simulated seawater. An Al/seawater battery has been fabricated directly using NF@Ni-BTC NFA as the cathode, showing higher power density, anode efficiency, and energy density than all the reported Al/H 2 O batteries measured in the electrolyte without addition of corrosion inhibitors. This work not only develops a low-cost, highly efficient noble-metal-free HER catalyst for high-performance Al/seawater batteries via facile and economical self-assembly strategy, but provides scientific insights for the self-assembly mechanism and high performance of the HER catalyst and the Al/seawater batteries.