Fe(III) Docking-Activated\nSites in Layered Birnessite\nfor Efficient Water Oxidation

Abstract

Non-noble metal catalysts for promoting the sluggish\nkinetics of\noxygen evolution reaction (OER) are essential to efficient water splitting\nfor sustainable hydrogen production. Birnessite has a local atomic\nstructure similar to that of an oxygen-evolving complex in photosystem\nII, while the catalytic activity of birnessite is far from satisfactory.\nHerein, we report a novel Fe-Birnessite (Fe-Bir) catalyst obtained\nby controlled Fe(III) intercalation- and docking-induced layer reconstruction.\nThe reconstruction dramatically lowers the OER overpotential to 240\nmV at 10 mA/cm² and the Tafel slope to 33 mV/dec, making\nFe-Bir the best of all the reported Bir-based catalysts, even on par\nwith the best transition-metal-based OER catalysts. Experimental characterizations\nand molecular dynamics simulations elucidate that the catalyst features\nactive Fe(III)–O–Mn(III) centers interfaced with ordered\nwater molecules between neighboring layers, which lower reorganization\nenergy and accelerate electron transfer. DFT calculations and kinetic\nmeasurements show non-concerted PCET steps conforming to a new OER\nmechanism, wherein the neighboring Fe(III) and Mn(III) synergistically\nco-adsorb OH* and O* intermediates with a substantially reduced O–O\ncoupling activation energy. This work highlights the importance of\nelaborately engineering the confined interlayer environment of birnessite\nand more generally, layered materials, for efficient energy conversion\ncatalysis.