Controllable synthesis of biomimetic wood stem nanoporous high entropy oxides catalysts for oxygen evolution reaction

Bubbles generated during the oxygen evolution reaction (OER) in water splitting readily adhere to the electrode surface, thereby impeding contact between the electrolyte and the active sites, thereby increasing the overpotential. Consequently, it is imperative to elucidate the bubble release behavior and engineer electrodes that facilitate faster bubble release. In this study, inspired by the wood stem of the Norway spruce, we synthesized a gradient nanoporous high-entropy oxide (GNP-HEO) electrode with a controllable pore size. The GNP-HEO, featuring a well-controlled gradient in pore size, is achieved through a straightforward strategy combining selective laser melting with selective phase dissolution. This unique gradient nanoporous structure not only facilitates bubble release but also diminishes the bubble shielding effect in OER, thereby enhancing electrocatalytic performance. The affect interaction of Al, Co, Cr, Fe, and Ni, coupled with the gradient nanoporous structure, yields exceptional OER performance, evidenced by an overpotential of 250 mV at a current density of 50 mA/cm² and a Tafel slope of 38.0 mV/dec in 1 M KOH. Density functional theory calculations confirm that the GNP-HEO adheres to the adsorbate evolution mechanism reaction pathway and exhibits significant stability. This work highlights a promising approach for the design and synthesis of high-performance OER electrocatalysts.