Among all noble metals, Ir has become popular for water reduction/oxidation due to its stability in both acidic and alkaline electrolytes. We find that Ir on vertical graphene (Ir-VG) is an all-round bi-functional catalyst. A high content of metallic Ir (Ir0) manifests as active catalytic sites supported by a superaerophobic vertical graphene surface designed to facilitate two-/four-electron transfer processes. This binder-free, nanoscale hybrid catalyst yields low overpotentials for the HER and OER in both acidic and alkaline media. With a minimal catalyst loading of 50 μg cm-2 for the HER, the catalyst delivers a current density of 10 mA cm-2 at overpotentials of 47 mV and 17 mV in acidic and alkaline media, respectively. For the OER, the catalyst achieves a current density of 10 mA cm-2 at overpotentials of 300 mV and 320 mV in acidic and alkaline media, respectively. This highly active bi-functional catalyst enables total water splitting at 1.58 V (acidic) and 1.57 V (alkaline) for 10 mA cm-2. Unlike other catalysts, Ir-VG shows good stability against corrosion with undiminished current density even at high potential in harsh acidic or alkaline environments over 24 h. This unprecedented, versatile catalyst offers an appealing, cost-effective noble-metal-based scheme for pH-independent water electrolysis.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT and Ministry of Education (No. 2016R1E1A1A01942649, 2018R1A5A6075964, 2018K1A4A3A01064272, and 2017R1A2B4002442).
© 2019 The Royal Society of Chemistry.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)