La and Mn-doped cobalt spinel oxygen evolution catalyst for proton exchange membrane electrolysis

Finding electrocatalysts using earth-abundant materials as a replacement
to iridium for oxygen-evolution reaction (OER) in proton exchange membrane
water electrolyzer (PEMWE) represents a critical step in reducing the cost
for green hydrogen production. We report here a nanofibrous cobalt spinel
catalyst co-doped with lanthanum and manganese prepared from zeolitic
imidazolate framework embedded in electrospun polymer fiber. The catalyst
demonstrated a low overpotential of 353 millivolts at 10 milliamperes per
square centimeter and a low degradation for OER over 360 hours in acidic
electrolyte. PEMWE containing this catalyst at anode demonstrated a
current density of 2000 milliamperes per square centimeter at 2.47 volts
(Nafion® 115 membrane) or 4000 milliamperes per square centimeter at 3.00
volt (Nafion® 212 membrane), and low degradation in
accelerated-stress-test. High-resolution electronic microscopy and
operando X-ray absorption spectroscopy, combined with computational
modeling, revealed the different functions of lanthanum, manganese, and
cobalt in enabling enhanced activity, conductivity and acidic tolerance
within the OER operating window.