Adaptive phosphorus modulation tailoring hydroxyl intermediate adsorption for ultrafast water splitting

Abstract

Addressing inadequate OH* adsorption in RuCo alloy catalysts is crucial for boosting intermediate coverage and redirecting the water-splitting pathway. Herein, the adaptive P sites were strategically incorporated to overcome the aforementioned challenge. The P sites, as potent OH* adsorption centers, synergize with Co sites to promote water dissociation and enrich surrounding Ru sites with H* intermediates, thus triggering the Volmer-Tafel route for hydrogen evolution reaction (HER). Besides, during the oxygen evolution reaction (OER), the surface of P-RuCo was reconstructed into Ru-doped CoOOH with anchored PO₄³⁻. These PO₄³⁻ not only circumvent the intrinsic OH* adsorption limitations of Ru-CoOOH in the adsorbate evolution mechanism (AEM) by rerouting to a more expeditious lattice oxygen oxidation mechanism (LOM) but also improve the coverage of key oxygen-containing intermediates, significantly accelerating OER kinetics. Consequently, the P-RuCo demonstrates exceptional bifunctional performance, with overpotentials of 29 mV for HER and 222 mV for OER at 10 mA cm⁻². Remarkably, the mass activities of P-RuCo for HER (5.48 A mg⁻¹) and OER (2.13 A mg⁻¹) are 6.2 and 11.2 times higher than those of its commercial counterparts (Ru/C for HER and RuO₂ for OER), respectively. When integrated into an anion-exchange-membrane electrolyzer, this catalyst achieves ampere-level current densities of 1.32 A cm⁻² for water electrolysis and 1.23 A cm⁻² for seawater electrolysis at 2.1 V, with a 500-h durability.