A survey of Earth-abundant metal oxides as oxygen evolution electrocatalysts in acidic media (pH < 1)

Abstract

A promising strategy to estabilize earth-abundant transition metal oxides during water electrolysis in acidic media to compete with noble metal water oxidation catalysts.

Mechanochemical synthesis and application of mixed-metal copper–ruthenium HKUST-1 metal–organic frameworks in the electrocatalytic oxygen evolution reaction

“…The faradaic efficiency (FE) was calculated by the method of Galán-Mascarós et al 68 (see Experimental section for details). Cu 10 Ru-BTC reached the highest FE with 70% from the tested samples, but the others are closely following with Cu 7 Ru-BTC FE = 68%, Cu 6 Ru-BTC FE = 66%, HKUST-1 FE = 64%, RuO 2 FE = 66% and bare NF FE = 61% (Table S7†).…”

“…Chronopotentiometry was conducted following the above electrochemical measurements. The current density was held at 10 mA cm −2 for 12 h. The FE was calculated according to the method of Galán-Mascarós et al , 68 with the exception of using a constant current of 50 mA cm −2 instead of 10 mA cm −2 . An Ocean Optics NeoFOX sensor system coupled with a FOSPOR probe was used to monitor the O 2 level in the electrochemical cell.…”

Dynamic Promotion of the Oxygen Evolution Reaction via Programmable Metal Oxides

“…(c) OER overpotential volcano at a current density of i OER = 10 mA cm –2 . Solid lines show microkinetic model results as a function of the reversible activation barrier ( E a eq ∈ [0.16, 0.66] eV); black ☆ are theoretical overpotentials predicted via DFT; pink markers − are experimentally measured overpotentials in acidic electrolyte (details, SI, Table S7).…”

“…Figure c depicts these simulated overpotential volcanoes (see SI, Figures S4 and S5 for reaction coordinates, coverages). Markers overlaid on the volcano plot compare both theoretical (black) and experimental (pink) − overpotentials for various oxide catalysts (see SI, Figure S6 for a magnified view near the volcano peak). Models with E a eq between 0.26 and 0.46 eV returned peak overpotentials (η i =10 peak ) of 229–451 mV (SI, Table S6), which is in the range of experimentally measured overpotentials of highly active OER catalysts in highly acidic electrolyte at this current density ( e.g., 220–260 mV for RuO x , , 373–458 mV for IrO x , − and 468 mV for CoO x ; see SI, Table S7).…”

“…Markers overlaid on the volcano plot compare both theoretical (black) and experimental (pink) − overpotentials for various oxide catalysts (see SI, Figure S6 for a magnified view near the volcano peak). Models with E a eq between 0.26 and 0.46 eV returned peak overpotentials (η i =10 peak ) of 229–451 mV (SI, Table S6), which is in the range of experimentally measured overpotentials of highly active OER catalysts in highly acidic electrolyte at this current density ( e.g., 220–260 mV for RuO x , , 373–458 mV for IrO x , − and 468 mV for CoO x ; see SI, Table S7). These E a eq values are also within the range of DFT calculations for AEM steps 3 and 4 on IrO 2 (0.36–0.54 eV and ∼0.4–0.5 eV, respectively), ,, but lower than reported for step 3 on RuO 2 (∼0.6 eV) .…”