Heterostructure boosts a noble-metal-free oxygen-evolving electrocatalyst in acid

Developing noble metal-free electrocatalysts (NMFEs) for the oxygen evolution reaction (OER) is tremendously challenging in acid. Despite extensive research efforts, few reported NMFEs can compete with Ru/Ir oxides for acidic OERs. Here, we report a heterostructure-engineering method to break the activity-stability limit of OER electrocatalysts and yield a noble-metal-free oxide that competes with RuO 2 in terms of OER specific activity and stability in acid. Via a set of correlative operando characterization techniques, heterostructured Co 3 O 4 /MnO 2 suppressed the in situ reconstruction of Co 3 O 4 and MnO 2 , and mitigated the electrochemical cycling-accelerated catalyst leaching, thus improving the acidic OER stability. Moreover, first-principles calculations supported that the synergy of Co and Mn in Co 3 O 4 /MnO 2 lowered the theoretical OER overpotentials. The optimized Co 3 O 4 /MnO 2 achieved an activity of 10 mA cm −2 at 319 ± 1.2 mV overpotential, and it demonstrated low degradation during the varying-current stability test (up to 200 mA cm −2 ) for 100 hours, making it among the best NMFEs for acidic OERs. Moreover, the promising performance of Co 3 O 4 /MnO 2 as the anodic catalyst was also validated in a proton-conducting membrane water electrolysis cell. This work breaks the activity-stability trade-off of noble metal-free OER electrocatalysts and yields a record performance in acid.