First report of vertically aligned (Sn,Ir)O2:F solid solution nanotubes: Highly efficient and robust oxygen evolution electrocatalysts for proton exchange membrane based water electrolysis

One dimensional (1D) vertically aligned nanotubes (VANTs) of (Sn0.8Ir0.2)O-2:10F are synthesized for the first time by a sacrificial template assisted approach. The aim is to enhance the electrocatalytic activity of F doped (Sn,Ir)O-2 solid solution electrocatalyst for oxygen evolution reaction (OER) in proton exchange membrane (PEM) based water electrolysis by generating (Sn0.8Ir0.2)O-2:10F nanotubes (NTs). The 1D vertical channels and the high electrochemically active surface area (ECSA similar to 38.46 m(2)g(-1)) provide for facile electron transport. This results in low surface charge transfer resistance (4.2 Omega cm(2)), low Tafel slope (58.8 mV dec(-1)) and excellent electrochemical OER performance with similar to 2.3 and similar to 2.6 fold higher electrocatalytic activity than 2D thin films of (Sn0.8Ir0.2)O-2:10F and benchmark IrO2 electrocatalysts, respectively. Furthermore, (Sn0.8Ir0.2)O-2:10F NTs exhibit excellent mass activity (21.67 A g(-1)), specific activity (0.0056 mAcm(-2)) and TOF (0.016 s(-1)), which is similar to 2-2.6 fold higher than thin film electrocatalysts at an overpotential of 270 mV, with a total mass loading of 0.3 mg cm(-2). In addition, (Sn0.8Ir0.2)O-2:10F NTs demonstrate remarkable electrochemical durability - comparable to thin films of (Sn0.8Ir0.2)O-2:10F and pure IrO2, operated under identical testing conditions in PEM water electrolysis. These results therefore indicate promise of (Sn0.8Ir0.2)O-2:10F NTs as OER electrocatalysts for efficient and sustainable hydrogen production.