Cu-BDC-derived hierarchically porous CuO for electrochemical charge storage and photoelectrochemical response

Hierarchically porous CuO was prepared by calcining a Cu-benzene-1,4-dicarboxylate (Cu-BDC)-containing precursor at 500 °C and compared with conventionally synthesized CuO. X-ray diffraction identified monoclinic tenorite CuO (JCPDS 00-002-1041) after calcination, while the uncalcined intermediate also contained reflections from fcc metallic Cu (JCPDS 04-0836). The precursor-derived CuO exhibited a BET surface area of 187 m² g^-1 and a pore volume of 0.81 cm³ g^-1, compared with 24 m² g^-1 and 0.07 cm³ g^-1 for pristine CuO. Analysis of the UV-vis absorption spectra using indirect-transition Tauc plots gave apparent transition energies of 2.3 and 2.4 eV for precursor-derived and pristine CuO, respectively. On 2.5 mm-diameter glassy-carbon working electrodes carrying 1.31 ± 0.05 mg of dried composite, precursor-derived CuO delivered 503 F g^-1 in 1 M Na₂SO₄ and 637 F g^-1 in 1 M KOH at 0.5 A g^-1 and showed the strongest charge-storage response among the tested materials. Under AM 1.5G illumination, the same material produced a larger anodic current and retained approximately 88% of its post-transient current over 2 h. These findings show that conversion of a Cu-BDC-containing precursor provides an effective route to porous CuO electrodes with improved charge-storage performance and a stronger photoelectrochemical response.