Water Splitting with an Enhanced Bifunctional Double
Perovskite
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Abstract
The
rational design of highly active and durable electrocatalysts
for overall water splitting is a formidable challenge. In this work,
a double perovskite oxide, i.e., NdBaMn<sub>2</sub>O<sub>5.5</sub>, is proposed as a bifunctional electrode material for water electrolysis.
Layered NdBaMn<sub>2</sub>O<sub>5.5</sub> demonstrates significant
improvement in catalyzing oxygen and hydrogen evolution reactions
(OER and HER, respectively), in contrast to other related materials,
including disordered Nd<sub>0.5</sub>Ba<sub>0.5</sub>MnO<sub>3−δ</sub> as well as NdBaMn<sub>2</sub>O<sub>5.5−δ</sub> and
NdBaMn<sub>2</sub>O<sub>5.5+δ</sub> (δ < 0.5). Importantly,
NdBaMn<sub>2</sub>O<sub>5.5</sub> has an OER intrinsic activity (∼24
times) and a mass activity (∼2.5 times) much higher than those
of the benchmark RuO<sub>2</sub> at 1.7 V versus the reversible hydrogen
electrode. In addition, NdBaMn<sub>2</sub>O<sub>5.5</sub> achieves
a better overall water splitting activity at large potentials (>1.75
V) and catalytic durability in comparison to those of Pt/C–RuO<sub>2</sub>, making it a promising candidate electrode material for water
electrolyzers. The substantially enhanced performance is attributed
to the approximately half-filled e<sub>g</sub> orbit occupancy, optimized
O p-band center location, and distorted structure. Interestingly,
for the investigated perovskite oxides, OER and HER activity seem
to be correlated; i.e., the material achieving a higher OER activity
is also more active in catalyzing HER
