Ir-O-Mn embedded in porous nanosheets enhances charge transfer in low-iridium PEM electrolyzers

Using metal oxides to disperse iridium (Ir) in the anode layer proves effective for lowering Ir loading in proton exchange membrane water electrolyzers (PEMWE). However, the reported low-Ir-based catalysts still suffer from unsatisfying electrolytic efficiency and durability under practical industrial working conditions, mainly due to insufficient catalytic activity and mass transport in the catalyst layer. Herein we report a class of porous heterogeneous nanosheet catalyst with abundant Ir-O-Mn bonds, achieving a notable mass activity of 4 A mg_Ir⁻¹ for oxygen evolution reaction at an overpotential of 300 mV, which is 150.6 times higher than that of commercial IrO₂. Ir-O-Mn bonds are unraveled to serve as efficient charge-transfer channels between in-situ electrochemically-formed IrO_x clusters and MnO_x matrix, fostering the generation and stabilization of highly active Ir³⁺ species. Notably, Ir/MnO_x-based PEMWE demonstrates comparable performance under 10-fold lower Ir loading (0.2 mg_Ir cm⁻²), taking a low cell voltage of 1.63 V to deliver 1 A cm⁻² for over 300 h, which positions it among the elite of low Ir-based PEMWEs.