The adoption of artificial intelligence (AI) technologies has been reported to affect various aspects of second language (L2) education in recent years. However, the interplay of AI and teacher professionalism has gained scant attention among researchers. To address the gap, this study employed a qualitative research design to examine the contribution of AI technologies to English as a foreign language (EFL) teachers' self-directed professional development (SDPD). A sample of 34 Chinese EFL teachers was interviewed individually. The results of manual thematic analysis showed four ways in which AI tools could foster Chinese EFL teachers' SDPD. Specifically, it was frequently declared that by 'providing access to latest resources and trends', 'reducing workload and pressure', 'fostering reflection and personalized instruction', and 'enhancing enthusiasm and novelty in teaching', AI technologies contributed to EFL teachers' passion for SDPD. A comprehensive discussion of the findings and implications for EFL teachers and teacher educators is presented to augment their AI literacy and passion for involving in and devising AI-mediated SDPD practices in L2 settings.