Theoretical-Interfacial Codesign Enabling a Multi-Functional Electrode for Efficient Electrocatalysis and Energy Storage

The strategic design of integrated catalysts for overall water splitting, urea electrolysis, and energy storage represents an unexplored frontier with significant challenges for catalyst engineering. Inspired by theoretical predictions that CoP/CoNi₂S₄ composites exhibit enhanced hydrogen evolution reaction (HER) activity compared to individual components, this nanorod structure was fabricated, demonstrating exceptional HER performance across acidic, alkaline, and simulated seawater conditions. It achieved 10 mA cm^-2 at overpotentials of 119 mV (acidic), 88 mV (alkaline), and 95 mV (seawater), with 100-h stability, surpassing commercial Pt/C at high current densities (200 mA cm^-2) with η₂₀₀ values of 232 mV (1 M KOH) and 234 mV (1 M KOH + 0.5 M NaCl). For oxygen evolution reaction (OER), it exhibited superior activity in alkaline media (η₁₀ = 267 mV) and simulated seawater, outperforming commercial RuO₂. In urea-added electrolytes, the symmetric electrolyzer required only 1.53 V to achieve 10 mA cm^-2. As a hybrid supercapacitor, the assembled CoP/CoNi₂S₄//AC device delivered an energy density of 50.9 Wh kg^-1 at 800 W kg^-1 with excellent cycling stability. This TMP/TMS composite integrates electrocatalytic and energy storage functionalities, paving the way for multifunctional applications in energy conversion technologies.