3R-delafossite CuGaO2 sample with high crystallinity and single phase was prepared by simple low-temperature hydrothermal method. The fundamental physicochemical properties of 3R-delafossite CuGaO2 were systematically studied by density functional theory calculations and experimental characterization. Through a series of characterization, analysis, (photo)electrochemical and photocatalytic activity testing, the as-prepared CuGaO2 samples exhibit the potential for hydrogen production and high photocatalytic degradation for tetracycline hydrochloride (TCH). Furthermore, CuGaO2 photoelectrode exhibits long-term stability and large photocurrent density. These observations suggest that 3R-delafossite CuGaO2 is a potential promising photocatalyst driven by visible-light. Finally, possible breakthrough directions of 3R-delafossite CuGaO2 photocatalyst are discussed.

Internal polarized electric field is found to be an effective and available strategy to separate photogenerated electron−hole pairs. By this method, the efficiency of photocatalytic reactions can be obviously enhanced. Here, the layered compound of BiOIO 3 with spontaneous polarization was synthesized by a simple hydrothermal method. Taking another bismuth compound BiOI as a counterpart, which has a similar layered structure, the spontaneous polarization effects of BiOIO 3 were analyzed and confirmed. The photocatalytic activity of BiOIO 3 and BiOI were evaluated by the degradation of methyl orange. Methyl orange was almost completely photocatalytically decomposed by BiOIO 3 and BiOI in 40 and 90 min, respectively. The separation and transfer behaviors of photogenerated electron−hole pairs were investigated by a series of photoelectrochemical characterizations. It is further proved the separation and transmission efficiency of BiOIO 3 are higher than those of BiOI. According to the results of density of theory calculations, the internal polarized electric field in BiOIO 3 is ascribed to the spatial asymmetry of the IO 3 group, which is estimated to ∼1.5 × 10 10 V/m. Under the action of this internal polarized electric field, the photogenerated electrons and holes would transfer along opposite directions, i.e., photogenerated electrons and holes respectively gather at the Bi/I side and O side. Additionally, superoxide radicals (•O 2 − ) and holes (h + ) are produced during the degradation process, which are responsible for the high visible-light photocatalytic activity. Finally, the cyclic degradation test proves that its photocatalytic performance has long-term stability. Therefore, BiOIO 3 polar material can be used as one of the alternative materials for efficient photocatalytic reaction.

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