Universal Synthesis of Amorphous Metal Oxide Nanomeshes.

Constructing the pore structures in amorphous metal oxide nanosheets can enhance their electrocatalytic performance by efficiently increasing specific surface areas and facilitating mass transport in electrocatalysis. However, the accurate synthesis for porous amorphous metal oxide nanosheets remains a challenge. Herein, a facile nitrate-assisted oxidation strategy is reported for synthesizing amorphous mesoporous iridium oxide nanomeshes (a-m IrO NMs) with a pore size of ∼4 nm. X-ray absorption characterizations indicate that a-m IrO NMs possess stretched Ir─O bonds and weaker Ir-O interaction compared with commercial IrO. Combining thermogravimetric-fourier transform infrared spectroscopy with differential scanning calorimetry measurements, it is demonstrated that sodium nitrate, acting as an oxidizing agent, is conducive to the formation of amorphous nanosheets, while the NO produced by the in situ decomposition of nitrates facilitates the generation of pores within the nanomeshes. As an anode electrocatalyst in proton exchange membrane water electrolyzer, a-m IrO NMs exhibit superior performance, maintaining a cell voltage of 1.67 V at 1 A cm for 120 h without obvious decay with a low loading (0.4 mg cm). Furthermore, the nitrate-assisted method is demonstrated to be a general approach to prepare various amorphous metal oxide nanomeshes, including amorphous RhO, TiO, ZrO, AlO, and HfO nanomeshes.