Journal of the Microelectronics and Packaging Society

광전기화학적 물분해에서 광전극으로 이용되는 GaN은 전해질에 대해 높은 안정성을 가지고 있으며 물의 산 화 환원준위를 포함하고 있어 외부전압 없이 물분해가 가능하다. 그러나 GaN 광전극의 경우, 재료 자체의 효율이 낮아 상용화하기에는 부족한 실정이다. 본연구에서는 광효율을 향상시키기 위해 Cobalt phosphate(Co-pi) 촉매를 광전기증착 (Photoelectro-deposition)방법을 통하여 GaN 광전극에 도입하였다. Co-pi 촉매 증착 후 SEM, EDS, XPS분석을 진행하 여 Co-pi의증착 여부및증착 정도를 확인하고, Potentiostat를이용해 PEC 특성을 분석하였다. SEM 이미지를 통해 Copi가 GaN 표면 위에 20~25 nm 사이즈의 클러스터 형태로 고르게 증착되어 있는 것을 확인하였다. EDS 및 XPS 분석을 통해 GaN 표면의입자가 Co-pi임을확인하였다. 이후측정된 PEC 특성에서 Co-pi를증착시킨후 0.5 mA/cm2에서 0.75 mA/cm2로향상된 광전류밀도 값을 얻을수있었다. 향상된 원인을 밝히기 위하여, 임피던스및 Mott-Schottky 측정을진 행하였고, 측정 결과, 50.35 Ω에서 34.16 Ω으로 감소한 분극저항(Rp)과증가된 donor 농도(ND) 값을 확인하였다. 물분해 전후, 표면 성분을 분석한 결과 물분해 후에도 Co-pi가남아있음으로써 Co-pi 촉매가 안정적이라는 것을 확인하였다. 이 를 통해, Co-pi가 GaN의 효율 향상을 위한 촉매로서 효과가 있음을 확인하였고, 다른 광전극에 촉매로써 적용시켰을 경 우, PEC 시스템의 효율을 향상시킬 수 있을 것으로 판단된다.
In the photoelectrochemical (PEC) water splitting, GaN is one of the most promising photoanode materials due to high stability in electrolytes and adjustable energy band position. However, the application of GaN is limited because of low efficiency. To improve solar to hydrogen conversion efficiency, we introduce a Cobalt Phosphate (Copi) catalyst by photo-electrodeposition. The Co-pi deposition GaN were characterized by SEM, EDS, and XPS, respectively, which illustrated that Co-pi was successfully decorated on the surface of GaN. PEC measurement showed that photocurrent density of GaN was 0.5 mA/cm2 and that of Co-pi deposited GaN was 0.75 mA/cm2. Impedance and Mott-Schottky measurements were performed, and as a result of the measurement, polarization resistance (Rp) and increased donor concentration (ND) values decreased from 50.35 Ω to 34.16 Ω were confirmed. As a result of analyzing the surface components before and after the water decomposition, it was confirmed that the Co-pi catalyst is stable because Co-pi remains even after the water decomposition. Through this, it was confirmed that Co-pi is effective as a catalyst for improving GaN efficiency, and when applied as a catalyst to other photoelectrodes, it is considered that the efficiency of the PEC system can be improved.

Keywords Gallium nitride, Photoelectrode, Oxygen Evolution Catalyst, Water splitting, Co-phosphate, Deposition, Photoelectrochemistry, Hydrogen generation