Fabrication of strong bifunctional electrocatalytically active hybrid Cu-Cu₂O nanoparticles in a carbon matrix

Herein, earth-abundant cost-effective hybrid copper-cuprous oxide nanoparticles have been fabricated in a carbon matrix (Cu-Cu₂ONPs@C) and used as bifunctional electrocatalysts for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). At a 0.1 mg loading, OER studies of Cu-Cu₂ONPs@C showed a significantly low overpotential of 530 mV @ 10 mA cm^-2 with the applied potential of 2.07 V in 0.4 M KOH. HER studies showed an overpotential of -672 mV @ 10 mA cm^-2 with the applied potential of -1.058 V in 0.4 M H₂SO₄. Cu-Cu₂ONPs@C showed a good electrocatalytic current density of 57.7 mA cm^-2 for OER and -125 mA cm^-2 for HER at a significantly low catalyst loading. For controlled studies, Cu₂ONPs and CuNPs in carbon matrix have also been synthesized, and their catalytic activities (OER and HER) have been compared with those of the hybrid Cu-Cu₂ONPs@C. The comparative studies indicated that the presence of conducting metal CuNPs along with Cu₂ONPs in the carbon matrix enhanced the electrocatalytic activity for both OER and HER as compared to that of pure Cu₂ONPs and CuNPs in the carbon matrix. Interestingly, the solvent used for fabricating different NP electrodes has also shown significant influence on the electrocatalytic current density. The synthesized hybrid Cu-Cu₂ONPs@C, Cu₂ONPs@C, and CuNPs@C were characterized using powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), high resolution transmission electron microscopy (HR-TEM), and BET analysis. To the best of our knowledge, the fabricated hybrid Cu-Cu₂ONP@C exhibited a strong bifunctional electrocatalytic response at a high current density with a low catalyst loading (0.1 mg) among the different Cu-based nanostructured catalysts explored for the water splitting reactions.