Thermo‐Electric Powered High Energy‐Density Hybrid Supercapattery for Driving Overall Water Splitting: A Novel Trifunctional Builder for Self‐Powered Hydrogen Production

Integrated electrochemical energy devices with multifunctionality are evolving as an auspicious way to lift up energy technology. However, the challenge is utilizing a single-electrode material for multifunctional applications is essential to minimize the manpower and overall cost of the system. Herein, a novel and cost-effective self-powered aqueous electrochemical energy device (SAEED) is proposed via integrating asymmetric supercapattery (ASD) and water-splitting (WS) devices utilizing Cu₃Mo₂O₉ (CMD) nanostructures on Ni-foam (prepared via hydrothermal method) as a trifunctional electrode. First, the Cu₃Mo₂O₉/Ni electrode is examined for the supercapacitor, which shows the faradaic-type of charge-storage behavior with a superior specific capacity of 588.88 mAh g^-1. The Cu₃Mo₂O₉ǁgraphene ASD is constructed, which shows high energy storage performance with high device capacitance and energy/power densities and 98% retention capacitance over 5000 cycles. Second, the electrocatalyst behavior of the Cu₃Mo₂O₉/Ni electrode is explored, which reveals impressive HER/OER performance with lower overpotential (HER-120 mV at 10 mA cm⁻²/OER-310 mV at 50 mA cm⁻²) values. As a proof-of-concept, an SAEED was developed that contains a thermoelectric generator, Cu₃Mo₂O₉ǁgraphene ASD, and a beaker-type electrolyzer operating at a voltage of 1.58 V to eliminate power loss and intermittent issues for sustainable and uninterrupted production of H₂.