Toward carbon neutrality, low-carbon synthesis routes for valuable chemicals are critically important. C4 hydrocarbons, which are key to the petrochemical industry, are currently produced through energy-intensive processes. Photocatalytic ethane coupling offers a green route from ethane to C4 hydrocarbons, but selectively activating inert C-H bonds (415 kJ/mol) over weaker C-C bonds (347 kJ/mol) by photocatalysis remains challenging. This work reports an effective strategy of Auδ+-Au relay-promoted charge transfer and the synergy of light irradiation (photons) and heating (mainly phonons) for inert C-H bond activation toward butane synthesis. Furthermore, femtosecond-nanosecond time-resolved spectroscopy analysis shows that Auδ+-Au relay remarkably accelerates hole transfer by 1000 times (from ∼nanosecond to ∼picosecond time scale), thus dramatically facilitating charge carrier separation. Together, the synergy of light irradiation (photons) and heating (mainly phonons), even with a gas hourly space velocity of 2,400,000 mL h-1 g-1 and a butane yield of 166.5 mmol/g/h (1665 μmol/h), has been achieved, which is 8.2-fold higher than that of Au/CeO2. A remarkable turnover number (410,000) with respect to Auδ+-Au clusters and a high selectivity (85%) for butane have also been obtained. Such an Au-Auδ+/CeO2 catalyst is also rather stable (≥100 h). Fundamentally, it is found that heating can remarkably enhance the coupling process, boosting butane production by 3.3 times. Overall, Auδ+-Au relay-promoted synergy of light irradiation and heating enables the highly selective activation of inert C-H bonds under mild conditions.