Experimental works have shown that doping ZnO nanosheets by the Al atom meaningfully increases their sensitivity toward HCHO gas. Here, we applied density functional theory calculations to study the Al-doping effect on the sensitivity of a ZnO nanosheet to HCHO gas, explaining the experimental results. We found that the pristine ZnO nanosheet weakly interacts with the HCHO with adsorption energy (E_ad) of −9.3 kcal/mol, and the sensing response (S) value of 2.2 at 623 K. After the Al-doping process, the E_ad and S values increase to −40.7 kcal/mol and 83.9, respectively, indicating an excellent agreement with the experimental results. We showed a relation between the HOMO-LUMO gap and the S value, confirming with the experimental results. Also, the proposed Al-doped ZnO nanosheet shows a good selectivity to HCHO gas at the presence of H₂, NH₃, C₂H₅OH, CO, and CH₄ gases. A short recovery time of 18 s is predicted for Al–ZnO-based sensor which is comparable with the experimental value of 26 s. Finally, we conclude that the Al-doping makes the ZnO nanosheet a promising HCHO gas sensor with a high sensitivity, an excellent selectivity, and short recovery time.

实验工作表明，通过 Al 原子掺杂 ZnO 纳米片可显着提高其对 HCHO 气体的敏感性。在这里，我们应用密度泛函理论计算来研究 Al 掺杂对 ZnO 纳米片对 HCHO 气体敏感性的影响，并解释了实验结果。我们发现原始的 ZnO 纳米片与 HCHO 相互作用较弱，吸附能 (E _ad ) 为 -9.3 kcal/mol，623 K 时的传感响应 (S) 值为 2.2。Al 掺杂过程后，E _ad和S值分别增加至-40.7 kcal/mol和83.9，表明与实验结果非常吻合。我们展示了 HOMO-LUMO 能隙与 S 值之间的关系，并与实验结果相证实。_{此外，所提出的Al掺杂ZnO纳米片在H 2}、NH ₃、C ₂ H ₅ OH、CO和CH ₄气体存在下对HCHO气体表现出良好的选择性。Al-ZnO 基传感器的恢复时间预计为 18 s，与 26 s 的实验值相当。最后，我们得出结论，Al 掺杂使 ZnO 纳米片成为一种有前途的 HCHO 气体传感器，具有高灵敏度、优异的选择性和短的恢复时间。