A deep understanding of the electricity generation mechanism from the interaction between water molecules and carbon material surfaces is attractive for next-generation water-based energy conversion and storage systems. Herein, an asymmetric generator was assembled based on functionalized carbon nanotubes films to investigate the relative contribution from various oxygen functional groups on carbon surface to the water-electrical performance. Experiments and calculations demonstrate that the electricity mainly originates from the water molecule adsorption by carboxyl groups and dissociation of functional groups on carbon surface, which leads to the formation of electrical double layers at interfaces. This device allows the electricity generation with a variety of water sources, such as deionized water, tap water, as well as seawater. In particular, the generator based on carboxyl carbon nanotubes can induce a voltage of over 200 mV spontaneously in natural seawater with the power density of about 0.11 mW·g⁻¹. High voltages can be achieved easily through the series-connection strategy to power electronic products such as a liquid crystal display. This work reveals the dominant role of carboxyl groups in carbon-based water–electricity conversion and is expected to offer inspiration for the preparation of carbon materials with high electrical performance.

Solar-driven interfacial evaporation (SDIE) is emerging as a promising pathway to solving the worldwide water shortage and water pollution. Nanomaterials (e.g., plasmonic metals, inorganic/organic semiconductors, and carbon nanomaterials) and related nanochemistry have attracted increasing attention for the solar-to-vapor process in terms of broadband absorption, electronic structure adjustment, and surface/interface chemistry manipulation. Furthermore, the assembly of nanomaterials can contribute to the mass transfer, heat management, and enthalpy regulation of water during solar evaporation. To date, numerous nano-enabled materials and structures have been developed to improve the solar absorption, heat management (i.e., heat confinement and heat transfer), and water management (i.e., activation, evaporation, and replenishment). In this review, we focus on a systematical summary about the composition and structure engineering of nanomaterials in SDIE, including size and morphology effects, nanostructure optimizations, and structure-property relationship decoupling. This review also surveys recent advances in nanochemistry (e.g., preparation chemistry and structural chemistry) deployed to conceptual design of nanomaterials. Finally, the key challenges and future perspectives of nanomaterials for solar evaporation are overviewed. This review aims at providing guidance for the design and construction of nanomaterials for high-efficiency SDIE on the basis of the aspects of materials science and chemical engineering.

Heteroatom doping carbon materials exhibit a huge application potential for energy storage devices (ESDs). Herein, interconnected N/P co-doped carbon nanocage (NP-CNC) was synthesized from pyrene molecules by using nano-MgO as template and melamine-phytic acid supramolecular aggregate as dopant coupled with KOH activation. The as-prepared NP-CNC possesses interconnected nanocages for electron transportation and abundant micropores for ion adsorption. Moreover, co-doped N/P species in NP-CNC provide active sites and additional pseudocapacitance. Consequently, NP-CNC as electrode material for symmetric supercapacitor exhibits a high gravimetric capacitance of 435 F·g⁻¹ at 0.05 A·g⁻¹, high volumetric capacitance of 274 F·cm⁻³ at 0.032 A·cm⁻³, and long cycle lifespan with 96.1% capacitance retention after 50,000 cycles. Furthermore, NP-CNC as cathode for zinc-ion hybrid supercapacitor delivers satisfactory energy and power densities of 130.6 Wh·kg⁻¹ (82.3 Wh·L⁻¹) and 14.4 kW·kg⁻¹ (9.1 kW·L⁻¹). This work paves a promising approach to the preparation of high capacitance NP-CNC for ESDs.