In addition, e-CNY cardholders don't have to worry about their consumption data being obtained and reused for big data-based commercial analysis purposes, Wang said.

"Considering these advantages, the e-CNY wallet card is not a transitional or compromised solution. On the contrary, it could become the preferred choice for small-value payments in the long term," says Wang. "More than 5,000 Hong Kong people have obtained digital renminbi consumption cards by Wednesday, and other district authorities have approached us to install self-service e-CNY card issuance machines."

E-CNY wallet cards are now accepted at more than 1,500 business venues on the mainland, including convenience stores, shopping malls, cinemas and hotels, and the list is growing.

The Hong Kong Monetary Authority has teamed up with the nation's Digital Currency Institute in conducting technical tests on cross-boundary use of the e-CNY app. The tests have entered the second phase, focusing on using the SAR's Faster Payment System to top up e-CNY wallets. Cross-boundary use of the e-CNY will increase financial connectivity in the Greater Bay Area and improve the efficiency and user experience of making cross-boundary payments.

The challenge, Wang points out, is that the issuance and promotion of physical cards require time and constant input. So, it's difficult to see the effect in the short term.

Wu Haifeng, director of the fintech research center at the Shenzhen Finance Institute, agreed that the wide application of digital renminbi cards on the mainland is a prerequisite for its popularity among Hong Kong visitors.