Heterojunction engineering powered by CIGS solar cells for boosted photocatalytic methane coupling

Methane activation under mild conditions remains one of the most challenging targets in solar-to-chemical conversion. Here, we report a photovoltaic-photocatalyst hybrid strategy that integrates a (Ag,Cu)(In,Ga)Se 2 (ACIGS) solar-cell absorber with a well-documented Au/TiO 2 photocatalyst to enhance photocatalytic oxidative coupling of methane. The ACIGS layer serves as an efficient light harvester and charge supplier, promoting charge transfer to the Au/TiO 2 catalytic layer. The resulting interfacial charge pumping suppresses overall charge recombination, increases charge-carrier availability at the catalytic interface, and facilitates both lattice-oxygen activation and oxygen reduction processes involved in methane conversion. As a result, the Au/TiO 2 -ACIGS catalyst achieves markedly enhanced CH 4 -to-C 2 H 6 performance, delivering ~4-fold (0.69 mmol g -1 h -1 ) and ~3-fold (2.51 mmol g -1 h -1 ) enhancement in batch and flow operations, respectively, compared to bare Au/TiO 2 deposited on glass. The catalytic plate also demonstrates excellent operational stability, enabled by an in-situ oxygen-looping mechanism that continuously regenerates active surface oxygen species. This work highlights the potential of photovoltaic absorbers as active charge-generation platforms for photocatalysis, extending their role beyond conventional solar-energy harvesting. More broadly, the results further open avenues for next-generation solar-cell-assisted photocatalytic platforms for methane upgrading or other key solar-to-fuel reactions.