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Title: Microstructural origin of selective water oxidation to hydrogen peroxide at low overpotentials: a study on Mn-alloyed TiO 2
One key objective in electrocatalysis is to design selective catalysts, particularly in cases where the desired products require thermodynamically unfavorable pathways. Electrochemical synthesis of hydrogen peroxide (H 2 O 2 ) via the two-electron water oxidation reaction (2e − WOR) requires a +0.54 V higher potential than four-electron O 2 evolution. So far, best-performing electrocatalysts require considerable overpotentials before reaching peak faradaic efficiency. We present Mn-alloyed TiO 2 coatings prepared by atomic layer deposition (ALD) and annealing as a stable and selective electrocatalyst for 2e − WOR. Faradaic efficiency of >90% at < 150 mV overpotentials was achieved for H 2 O 2 production, accumulating 2.97 mM H 2 O 2 after 8 hours. Nanoscale mixing of Mn 2 O 3 and TiO 2 resulted in a partially filled, highly conductive Mn 3+ intermediate band (IB) within the TiO 2 mid-gap to transport charge across the (Ti,Mn)O x coating. This IB energetically matched that of H 2 O 2 -producing surface intermediates, turning a wide bandgap oxide into a selective electrocatalyst capable of operating in the dark. However, the high selectivity is limited to the low overpotential regime, which limits the system to low current densities and requires further research into increasing turn-over frequency per active site.  more » « less
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Date Published:
Journal Name:
Journal of Materials Chemistry A
Page Range / eLocation ID:
18498 to 18505
Medium: X
Sponsoring Org:
National Science Foundation
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