Rational design of open hollow nanoboxes via Ru and B synergistic electronic modulation in cobalt phosphide for efficient oxygen evolution reaction

Abstract

Developing efficient and stable electrocatalysts for the oxygen evolution reaction (OER) is essential for alkaline water electrolysis. Herein, ruthenium-doped cobalt phosphide encapsulated in open hollow nanoboxes of boron-nitrogen-codoped carbon (Ru-CoP/BNC-1) was successfully synthesized via a three-step strategy. Structural characterization revealed that the synergistic effect between Ru and boron- nitrogen-codoped carbon quantum dots (BCQDs) facilitated the selective etching of the ZIF-67 precursor, leading to a unique nanostructure with abundant lattice distortions and a high specific surface area after phosphidation. X-ray photoelectron spectroscopy (XPS) and in situ Raman spectroscopy confirmed that Ru doping effectively modulates the electronic structure of Co, promoting the formation of high-valent cobalt species, while B doping facilitates surface reconstruction via interfacial effects and leaching during OER, thereby optimizing the reaction pathway. Electrochemical measurements demonstrated that the catalyst delivers outstanding OER performance under alkaline conditions, requiring an overpotential of only 227 mV at 10 mA cm-2 and a Tafel slope of 80.01 mV dec-1, outperforming most reported cobalt-based catalysts and even commercial RuO2. Moreover, the catalyst exhibited excellent stability, showing negligible decay after 117 h of continuous operation at 50 mA cm-2. Density functional theory (DFT) calculations further revealed that the co-doping of Ru and B synergistically reduces the free-energy barrier for the *O-to-*OOH step, improving the reaction kinetics. This work provides a novel strategy for designing high-performance cobalt-based electrocatalysts through multi-element synergy.