Co₃O₄ rod and sheet-like films with different crystal facet exposure and Co²⁺/Co³⁺ ratio are synthesized on Ti substrate through a facile hydrothermal method with the adjusting of hydrothermal pressure and duration. Low pressure and short hydrothermal duration is likely to obtain rod-like film with almost pure (220) facet exposure, while the sheet-like film with the mixture of (220) and (222) facets is formed with relatively high pressure. Moreover, the Co²⁺/Co³⁺ ratio is 2.067 for Co₃O₄ rods and 1.717 for Co₃O₄ sheets. The FT-IR and the XPS results indicate that the improvement of Co²⁺/Co³⁺ ratio possibly results from the doping of CO₃²⁻/OH⁻, and the introduction of oxygen vacancies. The films are employed as cathodes for electrocatalytic NO₃⁻-N reduction. Because of the larger electrochemical active area and the lower internal resistance, better conversion of NO₃⁻-N to NH₄⁺-N is obtained by Co₃O₄ sheets film at constant voltage condition. However, the results are opposite when the constant current is applied. The larger exposure of (220) facet and the more amount of Co²⁺ and oxygen vacancies result in the better NO₃⁻-N removal and NH₄⁺-N conversion kinetics of Co₃O₄ rods film than that of Co₃O₄ sheets.

通过调节水热压力和持续时间，通过简便的水热方法在Ti衬底上合成了具有不同晶面暴露和Co ²⁺ / Co ³⁺比的Co ₃ O ₄棒状和片状薄膜。低压和短的水热持续时间很可能获得具有几乎纯净的（220）小面暴露的棒状薄膜，而具有（220）和（222）小面的混合物的片状薄膜是在相对较高的压力下形成的。此外，将Co ²⁺ / Co的³⁺比为2.067为钴₃ ö ₄棒和1.717为钴₃ ö ₄床单。的FT-IR和XPS的结果表明，钴的改善²⁺ / Co的³⁺比可能从CO的掺杂导致₃ ^{2- /} OH ^- ，和引进氧空位。该膜用作用于电催化NO ₃ ^-- N还原的阴极。由于较大的电化学活性区域和较低的内部电阻，所以通过Co ₃ O _4可以将NO ₃ ^-- N更好地转化为NH ₄ ⁺ -N在恒定电压条件下将薄膜压成薄片。但是，当施加恒定电流时，结果相反。（220）面的暴露量越大，Co ²⁺和氧空位的数量越多，与Co ₃ O相比，Co ₃ O ₄棒膜的NO ₃ ^-- N去除和NH ₄ ⁺ -N转化动力学更好。₄张