Nanoscale palladium as a new benchmark electrocatalyst for water oxidation at low overpotential

There is an overwhelming desire to discover new catalytic materials for efficient water oxidation that perform at low overpotentials (below 1.50 V vs. RHE), and which exhibit tremendous stability along with high oxygen evolution reaction (OER) current density over a small potential window. However, it remains a challenge to establish a competent solar to fuel conversion system. We present here the first example of a nanoscale nanoporous Pd-derived benchmark material used as a highly stable and low overpotential electrocatalyst for water oxidation. The Pd electrocatalyst executes water oxidation at an onset potential of just 1.43 V vs. RHE; η = 200 mV. The catalyst also exhibits remarkable performance for OER, reaching a current density of 10 mA cm^-2 at 1.47 V (η = 240 mV), and with a current density of 100 mA cm^-2 achieved at only 1.63 V (η = 400 mV), which represents better OER activity than that of the benchmark IrO₂ electrocatalyst (301 mV and 313 mV required to drive a current density of 10 mAcm^-2). Furthermore, the catalyst demonstrates a Tafel slope of 40 mV dec^-1, a high mass activity of 560 mA mg^-1 (MA) and a large TOF value of 0.2 s^-1, and exhibits remarkable long-term stability for use in oxygen evolution experiments. A thin-film Pd electrocatalyst was obtained via the Aerosol-Assisted Chemical Vapor Deposition (AACVD) method on conducting surfaces. XRD and XPS analyses showed a phase-pure crystalline metallic Pd deposit. A surface morphology study revealed a nanoparticulate highly porous nanostructure. Our study reveals a straightforward method for the development of the first example of a Pd-derived nanoporous electrocatalyst for high-efficiency water oxidation and for chemical energy conversion.