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_x NMs) with a pore size of ∼4 nm. X-ray absorption characterizations indicate that a-m IrO_x NMs possess stretched Ir─O bonds and weaker Ir-O interaction compared with commercial IrO₂. 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 NO₂ 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_x NMs exhibit superior performance, maintaining a cell voltage of 1.67 V at 1 A cm^-2 for 120 h without obvious decay with a low loading (0.4 mg_catalyst cm^-2). Furthermore, the nitrate-assisted method is demonstrated to be a general approach to prepare various amorphous metal oxide nanomeshes, including amorphous RhO_x, TiO_x, ZrO_x, AlO_x, and HfO_x nanomeshes.