Tunable Energy Release in a Reversible Molecular Solar Thermal System

Molecular solar thermal (MOST) systems open application fields for solar energy conversion as they combine conversion, storage, and release in one single molecule. For energy release, catalysts must be controllable, selective, and stable over many operation cycles. Here, we present a MOST/catalyst couple, which combines all these properties. We explore solar energy storage in a tailor-made MOST system (cyano-3-(3,4-dimethoxyphenyl)-norbornadiene/quadricyclane; NBD′/QC′) and the energy release heterogeneously catalyzed at a Au(111) surface. By photoelectrochemical infrared reflection absorption spectroscopy (PEC-IRRAS) and scanning tunneling microscopy, we show that Au triggers the energy release with very high activity. Most remarkably, the release rate of the heterogeneously catalyzed process can be tuned by applying an external potential. Our durability tests show that the MOST/catalyst system is stable over 1000 storage cycles without any decomposition. The surface structure of the catalyst is preserved, and its activity decreases by only 0.1% per storage cycle.The authors acknowledge financial support from the Deutsche Forschungsgemeinschaft (DFG) (392607742) and additional support from the DFG (Collaborative Research Centre SFB 1452 Catalysis at Liquid Interfaces, Research Unit FOR 1878 “Functional Molecular Structures on Complex Oxide Surfaces”, projects 214951840, 322419553). They thank Andreas Leng and Andreas Hirsch for their contributions to the quantitative analysis and Lukas Fromm and Andreas Görling for estimating the particle radius of the NBD′. K.M.P. acknowledges support from the Swedish Research Council FORMAS, the Swedish Energy Agency, and European Union’s Horizon 2020 Framework Programme under grant agreement number 951801 for financial support.With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000917-S).Peer reviewe