Effect of the Calcination Temperature on the Hydrogen Photocatalytic Production Over p‐Type Delafossite CuCrO 2

ABSTRACT Herein, p‐type delafossite CuCrO 2 catalysts were synthesized at various calcination temperatures (900, 1000, 1100, and 1200 °C), then characterized and evaluated for hydrogen production through photocatalytic methods, with an optimization of the reaction medium. Their textural and structural characteristics were assessed using various physicochemical methods, including XRD, BET, SEM‐EDS, and XPS. Optical and electrochemical properties were also evaluated by UV–visible spectroscopy, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and capacitance‐potential measurements (Mott‐Schottky analysis). It was shown that calcination temperature has a significant effect on these structural, textural, optical, and electrochemical properties, as well as on the materials' reactivity. The 3‐R delafossite CuCrO 2 structure was obtained starting from 900 °C, with crystallite sizes almost independent of calcination temperature. Electrochemical studies confirmed the p‐type nature of all samples. Optical, physical, and photoelectrochemical parameters were correlated to construct the energy diagram for evaluating the CuCrO 2 delafossite's ability to produce H 2 . In a neutral medium (Na 2 SO 4 ), the best activity was attributed to the preparation calcined at 1200 °C (CC1200) attributed to its structural and electrochemical stability, while in a basic medium (NaOH), the catalyst calcined at 1100 °C (CC1100) produced the highest amount of H 2 , combining a small crystallite size and a bandgap conducive to efficient light absorption.