Single-atom Co dispersed on polyoxometalate derivatives confined in bamboo-like carbon nanotubes enabling efficient dual-site lattice oxygen mediated oxygen evolution electrocatalysis for acidic water electrolyzers

Abstract

The development of efficient and durable earth-abundant electrocatalysts for the acidic oxygen evolution reaction (OER) is crucial for the large-scale application of proton exchange membrane water electrolyzers (PEMWEs). Here, we report a novel amorphous Mo–Ce oxide supported single-atom Co (Co_SA-MoCeO_x) encapsulated in bamboo-like carbon nanotubes (BCTs) catalysts for the acidic OER. Operando X-ray absorption spectroscopy confirms that the Mo–Ce oxide can promote the transformation of Co²⁺ sites into Co³⁺–O sites with lower coordination number and abundant oxygen vacancies at a low voltage, leading to a dual-metal-site lattice oxygen-mediated (LOM) pathway with fast OER kinetics. Moreover, the confinement effect of BCTs on Co_SA-MoCeO_x can reduce the direct contact between the catalyst and the acid, thus improving its corrosion resistance. The optimized catalyst exhibits a low overpotential of 239 mV for the OER at 10 mA cm⁻² in 0.5 M H₂SO₄ and maintains exceptional stability for more than 60 hours in PEMWEs, representing one of the best non-noble metal catalysts. Density functional theory calculations show that the strong interaction between single-atom Co sites and Mo–Ce oxide reduces the adsorption energy barrier of the LOM pathway from 1.60 eV to 1.08 eV, and inhibits the dissolution of the support with the increased vacancy formation energy of Mo, thus improving the OER activity and stability of the catalyst in acid.