Decentralized electrosynthesis of hydrogen peroxide (H2O2) via oxygen reduction reaction (ORR) can enable applications in disinfection control, pulping and textile bleaching, wastewater treatment, and renewable energy storage. Transition metal oxides are usually not efficient catalysts because they are more selective to produce H2O. Here, it is shown that divalent 3d transition metal cations (Mn, Fe, Co, Ni, and Cu) can control the catalytic activity and selectivity of columbite nanoparticles. They are synthesized using polyoxoniobate (K7HNb6O19·13H2O) and divalent metal cations by a hydrothermal method. The optimal NiNb2O6 holds an H2O2 selectivity of 96% with the corresponding H2O2 Faradaic efficiency of 92% in a wide potential window from 0.2 to 0.6 V in alkaline electrolyte, superior to other transition metal oxide catalysts. Ex situ X-ray photoelectron and operando Fourier-transformed infrared spectroscopic studies, together with density functional theory calculations, reveal that 3d transition metals shift the d-band center of catalytically active surface Nb atoms and change their interactions with ORR intermediates. In an application demonstration, NiNb2O6 delivers H2O2 productivity up to 1 molH2O2 gcat−1 h−1 in an H-shaped electrolyzer and can yield catholytes containing 300 × 10−3 m H2O2 to efficiently decomposing several organic dyes. The low-cost 3d transition-metal-mediated columbite catalysts show excellent application potentials.
Bibliographical noteFunding Information:
C.L. and H.L. contributed equally to this work. This work is financially supported by the Australian Research Council under the Future Fellowships scheme (FT160100107) and Discovery Programme (DP180102210), and the Faculty of Engineering, of The University of Sydney under the Early Career Researcher Scheme. H.L. and G.H. acknowledge the Welch Foundation (F-1841) and the Texas Advanced Computing Center for computational resources.
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- Hydrogen peroxide
- Oxygen reduction reaction