Highly efficient and durable total water splitting using CoP/Co2P-C bifunctional electrodes with tunable phase interfaces

Bifunctional seawater electrolysis is limited by the activity–durability trade-off in chloride-containing media. Here, in-situ-grown Co-BTC MOF arrays on nickel foam were converted into self-supporting CoP/Co 2 P-C/NF electrodes, enabling controlled evolution Co 2 P-rich to CoP-rich compositions and identifying a favourable CoP/Co 2 P coexistence range. The continuous conductive carbon framework shortens charge-transport paths, maintains electrolyte–electrode contact, and supports rapid interfacial kinetics. Theoretical calculations indicate that the CoP/Co 2 P biphasic interface modulates intermediate adsorption, weakening Cl adsorption while favouring water-splitting-related intermediates, consistent with suppressed chlorine-related competition. At 10 mA cm −2 in 1.0 M KOH, the optimized electrode requires 31 mV for hydrogen evolution reaction (HER) and 180 mV for oxygen evolution reaction (OER), and drives overall water splitting at 1.47 V with stable operation over 100 h at 1.56 V. In 1.0 M KOH + seawater, it maintains low voltage and outperforms Pt/C||RuO 2 , providing a reproducible phase-ratio regulation strategy for non-precious bifunctional seawater electrolysis electrodes.