Widespread implementation of fuel cell technology has been hampered by challenges originating from the oxygen reduction reaction (ORR). Even the most advanced ORR catalysts present high overpotentials and poor selectivity for the reduction of O2 to H2O. A substantial amount of H2O2 is generated as a product of incomplete reduction. We developed a series of cost-effective cobalt-doped copper oxide (Cu[Co]Ox) catalysts supported on Au. These catalysts not only show lower overpotentials but also very high selectivity for the complete reduction of O2 to H2O. Specifically, Cu-rich compositions, such as Cu0.8Co0.2Ox/Au, demonstrated remarkable activity and > 97% selectivity for H2O over a sizeable potential range (1.0 – 0.6 V) relevant to ORR. These catalysts were found to even outperform Pt in both activity, selectivity, and performance stability. These catalysts have been investigated using in situ Raman Spectroscopy and X-Ray Photoelectron Spectroscopy. Our studies indicate that the doped materials have a Co-active site embedded within the CuOx framework. The resulting sites lower the free energy of the potential determining step and enhance yield for the complete reduction to H2O. Specifically, these catalysts preferentially cleave the O-O bonds result in high selectivity for the 4e pathway. Figure 1

Transition metal oxides form the basis of promising oxygen reduction electrocatalysts due to their low cost, high activity, and abundance on the planet. A new class of Co-doped CuOx (Cu[Co]Ox/Au)...

Transition metal oxides form the basis of promising oxygen reduction electrocatalysts due to their low cost, high activity, and abundance on the planet. A new class of Cu[Co]Ox/Au catalyst was found to exhibit high activity and selectivity for the complete reduction of oxygen to water. The Cu-rich composite Cu0.8Co0.2Ox/Au electrodes exhibited nearly 97.5 % selectivity for water compared to either CuOx/Au (80 %) or CoOx/Au (70 %). Cu0.8Co0.2Ox/Au exhibited higher activity, stability, and better selectivity over a wide potential range when compared to well-known ORR catalysts such as Pt. In situ Raman spectroscopy revealed that the introduction of Co into CuOx resulted in the formation of under-coordinated Co centers within CuOx frameworks. These under-coordinated Co centers act as active sites for the scission of O-O bonds resulting in preferential formation of 4e reduction products. The composite electrode also demonstrated a superior hydrogen peroxide reduction ability.