Manganese-based oxygen evolution catalysts boosting stable solar-driven water splitting: MnSe as an intermetallic phase

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2020-12, Vol.8 (47), p.25298-2535
• Main Authors: Sun, Mao, Gao, Rui-Ting, Liu, Xianhu, Gao, Rui, Wang, Lei
• Format: Article
• Language: English
• Subjects: Bismuth oxides; Catalysts; Durability; Hydroxides; Intermetallic phases; Iron; Manganese; Manganese dioxide; Manganese oxyhydroxides; Nickel; Oxidation; Oxygen; Oxygen evolution reactions; Reaction kinetics; Splitting; Vanadates; Water splitting
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d0ta09946e

In photoelectrochemical (PEC) water splitting, exploring highly active cocatalysts, especially Mn-based catalysts, is becoming more important in enabling a comparison of a number of Co-, Fe-, and Ni-based traditional cocatalysts in solar water oxidation. Herein, we for the first time synthesized an efficient Mn-based (oxy)hydroxide catalyst through MnSe as an intermetallic phase. As iron was further incorporated into the MnSe, the MnFeSe electrode showed an outstanding oxygen evolution reaction (OER) activity (an overpotential of 247 mV at 10 mA cm −2 ) and reaction kinetics (a Tafel slope of 35 mV dec −1 ). The MnFeSe was electrochemically converted to Se-incorporated MnFe (oxy)hydroxides under oxidative potential during the OER. Remarkably, the novel Mn-based multi-metal catalyst was applied to BiVO 4 for solar-driven water splitting. The resulting photoelectrode exhibited a current density of 4.85 mA cm −2 at 1.23 V RHE in 1 M KBi under AM 1.5G illumination. More importantly, a 20 h durability was achieved owing to avoiding the photocorrosion of BiVO 4 , which is so far the best PEC performance using a highly active Mn-based cocatalyst compared to the common MnO x . Further DFT calculations on models of MnSe, MnFeSe, MnOOH, Se,Fe-MnOOH, MnO 2 , and Se,Fe-MnO 2 explained well the OER/PEC experimental results. This work developed a new strategy for designing and exploring advanced cocatalysts for a practical solar-driven water splitting system. An efficient Mn-based (oxy)hydroxide catalyst was formed through MnSe as an intermetallic phase, and applied to BiVO 4 boosting solar-driven water splitting. This new strategy could help develop more stable Mn-based oxygen evolution catalysts in photoelectrochemical systems.