Abstract:
Toward the development of sustainable and clean
energy sources for the replacement of fossil fuels, strategies for
constructing highly effective and durable trifunctional oxide
electrocatalysts with zero emission carbon is a key step for
boosting energy technologies through overall water splitting,
regenerative fuel cells, and metal−air batteries. Here, two
disordered ruthenate double-perovskites Ca2ScRuO6 (CSR) and
CaSrScRuO6 (CSSR) were synthesized by the conventional hightemperature solid-state reaction method, and their trifunctional
electrocatalytic behaviors for the oxygen reduction reaction (ORR)
and oxygen and hydrogen evolution reactions (OER/HER) were
investigated in alkaline medium (1 M KOH). The orthorhombic
(space group Pbnm) crystal structures of both CSR and CSSR were
refined from the neutron and laboratory X-ray powder diffraction data. The oxidation states of Ru cations in both compounds were
shown to be predominantly Ru+5, confirmed by X-ray photoelectron spectroscopy studies. The as-prepared bulk perovskites showed
excellent ORR performance with an onset potential of ∼0.89 V for CSR and 0.90 V vs reversible hydrogen electrode (RHE) for
CSSR, respectively. In addition, both compounds showed significantly low overpotentials toward OER (353 and 323 mV) and HER
(313 and 275 mV) at a current density of 10 mA cm−2
, demonstrating them to be active trifunctional electrocatalysts. The
substitution of an alkaline earth metal at the A-site introduces a synergistic effect of structural distortion and electronic properties of
Ru+5 metal ions responsible for enhanced trifunctional electrocatalytic activities. Such trifunctional catalytic behaviors of CSR and
CSSR materials can be further understood by density functional theory (DFT) calculations. The present finding not only provides
insight into the catalytic activity of these materials but also presents an example of efficient trifunctional bulk-phase oxide
electrocatalysts for practical applications.
