Temperature effect on n-Si/Fe/NiFe photoanodes for the high-efficiency PEC water splitting

Sunlight-driven photoelectrochemical cell (PEC) can utilize water for high-efficiency artificial photosynthesis to produce low-cost green hydrogen fuel. It is crucial to explore the factors affecting the efficiency of PEC water splitting. The ambient temperature of the electrode is yet an important factor that influences PEC performance. Here, n-Si/Fe/NiFe composite photoanodes prepared by electrodeposition exhibited a low onset potential of 0.87 V and a high photocurrent density of 29.70 mA cm⁻² (1.23 V vs. RHE) at room temperature, which is superior to those of n-Si/Fe and n-Si/NiFe. The influence of the temperature on the photoelectrochemical properties of n-Si/NiFe was systematically investigated. As the temperature increased, the photocurrent density of n-Si/Fe/NiFe decreased gradually and the oxidation reaction slowed down. Further experiments showed that raising the temperature helps to reduce the interfacial charge transfer resistance, increase the redox potential and carrier density. However, increasing the temperature also increases the recombination rate of photo generated carriers, reduces the carrier lifetime, and thus lowers the performance of PEC. Therefore, adjusting the ambient temperature is a potential method to improve the photoelectrochemical performance of silicon-based photoanodes.