Methanol has been proposed as an energy storage medium to replace fossil fuels because of its high hydrogen content (12.6 wt%), wide availability, low cost and high safety. On-site hydrogen production from methanol has therefore emerged as a promising approach to meet end-user demands while alleviating the challenges associated with hydrogen transportation and storage. Meanwhile, formaldehyde (HCHO) is an essential feedstock for the production of industrial resins and plastics, but its conventional manufacture relies on high-temperature methanol oxidation under harsh reaction conditions, producing large amount of wastewater. Therefore, the efficient and green conversion of methanol to H2 and formaldehyde without wastewater production offers an attractive and potentially profitable alternative pathway.
Photocatalysis provides a sustainable and green route for chemical transformations under mild conditions, but methanol conversion to H2 and HCHO is still limited by inefficient charge transport and sluggish surface reaction kinetics. To overcome these limitations, we have establithed a photon-phonon co-driven catalysis (PPCC) strategy, in which phonons promote the migration of photogenerated polarons while simultaneously accelerating surface reactions. This coupling of photon-driven activation and phonon-assisted processes can thus overcome the activity and selectivity limitations of conventional photocatalysis and thermocatalysis.
Within this framework, we designed a Li-modulated Pt single-atom catalyst, PtLi2-TiO2, which achieves an H2 production rate of 4.36 mol g-1 h-1 at 150 °C under 365 nm illumination, together with an apparent turnover frequency of 275,000 h-1 and 94% HCHO selectivity. Compared with representative low-temperature thermocatalytic systems for methanol conversion, PtLi2-TiO2 delivers an approximately one-order-of-magnitude higher H2 production rate (Figure 1a). More importantly, the system achieves an overall quantum yield (OQY) of 184%, surpassing the conventional 100% quantum-efficiency ceiling of purely photon-driven photocatalysis thanks to a chain reaction pathway. To evaluate its practical durability under intermittent operating conditions, the catalyst was subjected to repeated day-night cycles with 8 h of irradiation followed by 16 h of darkness each day. PtLi2-TiO2 maintains stable H2 production for 19 days and retains >94% HCHO selectivity (Figure 1b). In addition, a concentrated HCHO solution of 21.2 wt% is obtained in a batch reactor (Figure 1c).
Further investigation identifies Pt2+ as the primary active site for H2 evolution (Figure 2). Li regulates the local coordination and electronic environment of Pt to form a stable PtLi2 microenvironment, which favors highly dispersed Pt2+ single atoms and suppresses their aggregation during the reaction. Li also facilitates photoelectron transfer from TiO2 to Pt and weakens H adsorption, thereby promoting H2 formation and release. These effects collectively stabilize the active Pt2+ sites and enhance charge transfer and catalytic performance.
The roles of phonons in both charge transport and surface reactions were revealed by TAS, EPR and in situ DRIFTS. Temperature-dependent TAS shows that phonons promote polaron migration to the surface, enabling electron transfer to Pt2+ sites for H2 evolution. EPR identifies ·CH2OH as the key intermediate, while in situ DRIFTS shows its further dehydrogenation to HCHO upon heating. Together, these results establish a cascade in which photons initiate methanol activation, whereas phonons promote carrier migration and subsequent dehydrogenation, accounting for an OQY exceeding 100% (Figure 3) .
More importantly, this study establishes a systematic PPCC framework for alcohol dehydrogenation, connecting charge transport, surface chemistry and reactor-level performance within a single catalytic concept. This integrated picture not only deepens the understanding of photon-phonon cooperation, but also points toward broader applications of dual-energy-field catalysis and its potential translation to large-scale chemical processes.