Construction of Ternary Gallium-Based Liquid Metal/CuO-NiO Nanocomposite and Photocatalytic Degradation of Methylene Blue

The unique chemical and physical properties of Ga-based liquid metal (Ga-LM) interfaces present an intriguing platform for the in situ synthesis of novel composites. Mechanical shearing can effectively disperse bulk Ga-LM into micro/nanosized droplets, significantly increasing their interfacial area and enhancing their reactivity. Herein, we report the room-temperature, one-step fabrication of a novel ternary Ga-LM/CuO-NiO heterojunction through the interaction between liquid metal micro/nano droplets and an alkaline solution containing cupric sulfate and nickel nitrate, leading to the simultaneous formation of CuO and NiO. The morphology, elemental composition, chemical states, and crystallographic structure were comprehensively characterized with XPS, SEM, TEM, and XRD. The proposed mechanism for CuO and NiO formation on the LM interface involves the adsorption of [HGaO₃]^2- species at the interface, which subsequently react with [Cu(NH₃)₄]²⁺ and [Ni(NH₃)₆]²⁺ complexes concurrently formed in an ammonia solution. This reaction leads to the in situ formation and growth of CuO and NiO nanosheets directly on the LM interface. Band gap analysis shows that the Ga-LM/CuO-NiO composite possesses a narrower band gap (4.74 eV) than the LM (5.64 eV) and LM/CuO (5.48 eV) composites. Finally, the photocatalytic performance was investigated in the degradation of methylene blue, showing an excellent degradation efficiency of 97.1% over the Ga-LM/CuO-NiO composite within 110 min under simulated sunlight. The photodegradation rate constant over the Ga-LM/CuO-NiO composite is 16.5 and 3.4 times higher than those over the LM and LM/CuO composite, respectively. The significant photocatalytic performance of the Ga-LM/CuO-NiO composite is attributed to the synergistic effect of its three components. The brilliant structural stability and reusability of the composite were also confirmed. This study not only introduces a novel synthetic route for Ga-LM-based functional composites but also underscores the immense potential of the reactive Ga-LM interface as a versatile platform for designing advanced materials with enhanced performance, particularly in photocatalytic applications.