Atomic layer deposition of Ir nanostructures on carbon papers for alkaline hydrogen evolution: A binder-free electrode approach

Herein, we demonstrate the Ir growth on conductive carbon paper (CP) by Atomic Layer Deposition (ALD) for the preparation of HER electrocatalysts with precise control over the Ir loading and morphology, from single atoms to nanoparticles. Importantly, ALD electrode fabrication circumvents intermediate nanoparticle synthesis, transfer, and binder application steps, required for conventional sample preparation methods, allowing single step fabrication process. The electrocatalytic activity of the resulting Ir/CP electrodes was assessed in alkaline media (KOH) towards HER by the systematic variation of the number of ALD cycles. The results suggested the electrocatalytic performance to be an interplay between different catalytic parameters including, electrochemically active surface area, turnover frequency and mass activity. In particular, the Ir/CP electrode decorated with 300 Ir cycles exhibited superior catalytic performance, namely, lowest overpotential (32.7 mV), Tafel slope (80.6 mV dec -1 ), and minimal charge transfer resistance (0.7 Ω). A stability test for 60 h revealed a partial surface oxidation and Ir aggregation, yet it did not affect significantly the catalytic performance (∼15 mV increase in overpotential value). Overall, we present the ALD fabrication of Ir/CP electrodes as an efficient and durable HER catalyst in alkaline media, demonstrating the potential of ALD for designing high performance binder-free electrodes.