그래핀 탄화질소(g-C3N4) 광촉매는 밴드갭이 2.80 eV의 상대적으로 낮은 밴드갭을 가져 가시광선 영역에서 활성화

될 수 있으며, 탄소-질소 원자 간의 강한 공유결합으로 인해 열화학적 안전성이 우수하다. 그러나 g-C3N4가 가시광선

광촉매로 사용되기 위해서는 아직 밴드갭이 크다는 문제점이 있다. 본 연구에서는 이를 극복하기 위하여 melamine을

출발물질로 사용하여 520°C의 고온 반응에 의해 g-C3N4 광촉매를 합성하고, 여기에 알칼리 금속 수산화물(LiOH,

NaOH, KOH)을 첨가한 후 다시 500°C에서 열처리하여, 알칼리 금속 이온이 도핑된 M-g-C3N4 광촉매를 합성하였다.

그 후 FT-IR, XPS, XRD, UV-Vis spectrometer 등의 다양한 분석 기기를 사용하여 광촉매의 물리적 및 화학적 특성을

평가하였다. XRD 분석에서 27.5°에서의 강한 피크를 확인하였고, 이 결과로 부터 성공적으로 g-C3N4 광촉매가 합성

되었음을 알 수 있었다. 또한 알칼리 금속이 도핑된 M-g-C3N4 광촉매들은 알칼리 금속이 도핑되지 않은 g-C3N4 광촉

매의 2.80 eV에 비해 더 낮은 밴드갭을 가지며, 그중에서도 K 금속을 도핑 시 밴드갭 에너지가 2.56 eV로 가장 낮아

지는 것을 알 수 있었다. 밴드갭 에너지가 감소할수록 낮은 에너지의 광을 통해서도 광여기에 의해 전자와 정공을 쉽

게 발생시킬 수 있으므로, 본 연구를 통해 개발된 알칼리 금속으로 도핑된 M-g-C3N4 광촉매들은 효과적인 가시광선

광촉매로서 사용될 수 있다고 판단된다.

Graphene-based carbon nitride (g-C3N4) photocatalyst has a relatively narrow band gap of 2.80 eV, which

makes it active in the visible light range. Furthermore, the strong covalent bonds between carbon and nitrogen atoms

provide excellent thermochemical stability. However, g-C3N4 photocatalyst still has a high band gap, which hinders its use

as a visible light photocatalyst. To overcome this limitation, in this study, melamine was used as a starting material and the

g-C3N4 photocatalyst was synthesized by a high-temperature reaction at 520°C. To this, alkali metal hydroxides (LiOH,

NaOH, KOH) were added, respectively, followed by heat treatment at 500°C to synthesize alkali metal ion-doped M-g-

C3N4 photocatalysts. The physical and chemical properties of the photocatalysts were then evaluated using various analytical

equipments, including FT-IR, XPS, XRD, and UV-Vis spectrometer. XRD analysis confirmed a strong peak at 27.5°,

which indicated that the g-C3N4 photocatalyst was successfully synthesized. In addition, the alkali metal-doped M-g-C3N4

photocatalysts had narrower band gaps than the alkali metal-free g-C3N4 photocatalyst (2.80 eV), and among them, the

band gap energy was found to be the lowest at 2.56 eV when K metal was doped. As the band gap energy decreases, electrons

and holes can be easily generated by photoexcitation even with low-energy light, so it is judged that the alkali metaldoped

M-g-C3N4 photocatalysts developed through this study can be used as effective visible-light photocatalysts.

Graphene-based carbon nitride, Alkali metal doping, Band gap energy, Visible light photocatalyst

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