State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, College of Energy Engineering, Zhejiang University, Hangzhou, Zhejiang Province 310027, China.
Analyst. 2017 Dec 18;143(1):106-115. doi: 10.1039/c7an01051f.
The development of formaldehyde (HCHO) sensors employing reduced graphene oxide (rGO) as sensing materials calls for a profound, atomic level understanding on the roles of oxygen-containing groups. In this work, the performances of rGO-based HCHO sensors were investigated using ab initio calculations and experimental validation. Density functional theory (DFT) simulations were performed to calculate the adsorption energy (E) and charge transfer (ΔQ) for the adsorption of HCHO on pristine graphene, rGO with epoxides, rGO with hydroxyl groups, and rGO with carboxyl groups. The results show that the incorporation of oxygen-containing groups leads to an obvious increase of E and ΔQ values, with an order of carboxyl group > hydroxyl group > epoxides > pristine graphene. The increase of E and ΔQ values could increase the variation in the concentration of charge carriers, the change of conductance of the sensing materials, and hence the sensor response. The experimental measurements indicate that with a decrease in the C/O atomic ratio from 16.2 to 6.6, the sensor response to 1 ppm HCHO increases from 0.10% to 0.73%, confirming the DFT calculation results. Moreover, even with a certain C/O atomic ratio of ∼6.6, rGO with 6.80% carboxyl groups exhibits a distinctly larger response to 0.2-3 ppm HCHO, compared with the counterpart with 3.09% carboxyl groups. The as-obtained insights into the effects of oxygen-containing groups on the response of rGO to HCHO could be instructive for preparing rGO-based HCHO sensors for advanced performances.
采用还原氧化石墨烯（rGO）作为传感材料的甲醛（HCHO）传感器的发展需要深入了解含氧基团的作用。在这项工作中，使用从头算计算和实验验证研究了基于 rGO 的 HCHO 传感器的性能。密度泛函理论（DFT）模拟用于计算 HCHO 在原始石墨烯、具有环氧化物的 rGO、具有羟基的 rGO 和具有羧基的 rGO 上吸附的吸附能（E）和电荷转移（ΔQ）。结果表明，含氧基团的掺入导致 E 和ΔQ 值的明显增加，其顺序为羧基>羟基>环氧化物>原始石墨烯。E 和ΔQ 值的增加可以增加载流子浓度的变化、传感材料的电导变化，从而增加传感器的响应。实验测量表明，随着 C/O 原子比从 16.2 降低到 6.6，传感器对 1 ppm HCHO 的响应从 0.10%增加到 0.73%，证实了 DFT 计算结果。此外，即使在一定的 C/O 原子比为∼6.6 的情况下，具有 6.80%羧基的 rGO 对 0.2-3 ppm HCHO 的响应也明显大于具有 3.09%羧基的 rGO。对含氧基团对 rGO 对 HCHO 响应的影响的深入了解，可为制备具有先进性能的基于 rGO 的 HCHO 传感器提供有价值的指导。
