Low-grade heat (below 373 K) is abundant and ubiquitous, but mostly wasted due to the lack of cost-effective recovery technologies. The liquid-state thermocell (LTC), an inexpensive and scalable thermoelectric device, may be commercially viable for harvesting low-grade heat energy if its Carnot-relative efficiency (ηr) reaches ~5%, which is a challenging metric to achieve experimentally. We used a thermosensitive crystallization and dissolution process to induce persistent concentration gradient of redox ions, a highly enhanced Seebeck coefficient (~3.73 mV K–1), and suppressed thermal conductivity in LTCs. As a result, we achieved a high ηr of 11% for LTCs near room temperature, and a substantially decreased cost-performance of our LTC. Our device demonstration offers promise for cost-effective low-grade heat harvesting.

Two-dimensional (2D) oxides have unique electrical, optical, magnetic, and catalytic properties, which are promising for a wide range of applications in different fields. However, it is difficult to fabricate most oxides as 2D materials unless they have a layered structure. Here, we present a facile strategy for the synthesis of ultrathin oxide nanosheets using a self-formed sacrificial template of carbon layers by taking advantage of the Maillard reaction and violent redox reaction between glucose and ammonium nitrate. To date, 36 large-area ultrathin oxides (with thickness ranging from ~1.5 to ~4 nm) have been fabricated using this method, including rare-earth oxides, transition metal oxides, III-main group oxides, II-main group oxides, complex perovskite oxides, and high-entropy oxides. In particular, the as-obtained perovskite oxides exhibit great electrocatalytic activity for oxygen evolution reaction in an alkaline solution. This facile, universal, and scalable strategy provides opportunities to study the properties and applications of atomically thin oxide nanomaterials.

Solar‐driven interfacial evaporation by localization of solar heating at the air–liquid surface has emerged as a cost‐effective desalination technology. The rapid interfacial evaporation induces simultaneous salinity and temperature gradient between evaporation surface and bulk water, which enables electricity generation but is not comprehensively utilized. Herein, the combination of a thermogalvanic cell (TGC) and reverse electrodialysis (RED) in solar‐driven interfacial evaporation is proposed to extract energy from temperature and salinity gradients simultaneously. Because of the synergistic ion transport effect, the coupling of TGC and RED enables mutual power enhancement by orders of magnitude based on the rational spatial layout and the fabrication of composite electrodes. Finally, a steam‐electricity cogeneration system is designed, which achieves the 1.4 kg m−2 h−1 vapor and 1.11 W m−2 electricity simultaneously under one sun illumination. This concept opens a promising avenue towards a solar‐driven water‐energy nexus.