Iron-Anchored Black Phosphorus with 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 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 nanosheets (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 NS demonstrates high OER catalytic activity with low overpotentials of 240 mV at 10 mA cm-2, 379 mV at 1000 mA cm-2, and a Tafel slope of 24.2 mV dec-1. Experimental results and in situ spectroscopy characterizations confirm that the phosphate species generated by electro-oxidation of the electron-rich BP support act as proton reservoirs, decoupling the PCET step of adsorbate evolution mechanism (AEM) and transforming the rate-determining step (RDS) from *O to *OOH into *OOH deprotonation step. Meanwhile, the anchored Fe sites accelerate the formation of *OOH, ultimately achieving the boosted OER process.