Iron-anchored black phosphorus with a phosphate proton reservoir for industrial-current-density water oxidation

Abstract

Black phosphorus (BP)-based electrocatalysts exhibit potential applications in water oxidation due to the unique two-dimensional (2D) structure and electronic properties. Nevertheless, low intrinsic catalytic activity and the sluggish multi-step proton-coupled electron transfer (PCET) reaction limit the performance of BP-based oxygen evolution reaction (OER) electrocatalysts. Herein, we report an Fe-anchored BP nanosheet (Fe/BP NS) catalyst synthesized via electrochemical exfoliation to fully expose active sites while anchoring Fe sites for efficient OER. Benefiting from the 2D nanosheet structure with rapid electron transfer ability, Fe/BP NSs demonstrate high OER catalytic activity with low overpotentials of 240 mV at 10 mA cm⁻² and 379 mV at 1000 mA cm⁻², and a Tafel slope of 24.2 mV dec⁻¹. Experimental results and in situ spectroscopy characterization studies confirm that the phosphate species generated by electro-oxidation of the electron-rich BP support act as proton reservoirs, decoupling the PCET step of the adsorbate evolution mechanism (AEM) and transforming the rate-determining step (RDS) from *O to *OOH into the *OOH deprotonation step. Meanwhile, the anchored Fe sites accelerate the formation of *OOH, ultimately achieving the boosted OER process.