• Energy Research

AbstractDue to the growing demand for clean and renewable hydrogen fuel, there has been a surge of interest in electrocatalytic water‐splitting devices driven by renewable energy sources. However, the feasibility of self‐driven water splitting is limited by inefficient connections between functional modules, lack of highly active and stable electrocatalysts, and intermittent and unpredictable renewable energy supply. Herein, we construct a dual‐modulated three‐dimensional (3D) NiCo2O4@NiCo2S4 (denoted as NCONCS) heterostructure deposited on nickel foam as a multifunctional electrode for electrocatalytic water splitting driven by photovoltaic‐powered supercapacitors. Due to a stable 3D architecture configuration, abundant active sites, efficient charge transfer, and tuned interface properties, the NCONCS delivers a high specific capacity and rate performance for supercapacitors. A two‐electrode electrolyzer assembled with the NCONCS as both the anode and the cathode only requires a low cell voltage of 1.47 V to achieve a current density of 10 mA cm−2 in alkaline electrolyte, which outperforms the state‐of‐the‐art bifunctional electrocatalysts. Theoretical calculations suggest that the generated heterointerfaces in NCONCS improve the surface binding capability of reaction intermediates while regulating the local electronic structures, which thus accelerates the reaction kinetics of water electrolysis. As a proof of concept, an integrated configuration comprising a two‐electrode electrolyzer driven by two series‐connected supercapacitors charged by a solar cell delivers a high product yield with superior durability.

Abstract Lithium-air batteries have attracted extensive attention in the general energy field. To enhance the practical applicability of lithium-air batteries, the overpotential caused by the diffusion of oxygen in the cathode, a significant component of the total overpotential, should be well comprehended. In this work, a wetted model is derived to evaluate the energy loss associated with liquid electrolytes. The oxygen diffusion in both electrolytes and porous cathodes is investigated systematically by taking oxygen concentration distribution into account. By analyzing the factors associated with cathode overpotential, such as the cathode thickness of and the viscosity of electrolyte, our work facilitates the improvement in the electrochemical performance of lithium-air batteries.

While passive radiative cooling has shown great potential in temperate regions in lowering surface temperatures, its cooling performance under tropical climate that is characterised by high solar irradiance and humidity still lacks exploration. Herein, we adopt a highly reflective polymeric coating with BaSO4 particles dispersed in P(VdF-HFP) matrix for radiative cooling in the tropics. Through the strong Mie scattering of sunlight and intrinsic bond vibration, the substrate-independent average solar reflectance and infrared emittance within the 8–13 μm atmospheric window could reach 97% and 94.2%, respectively. For the first time, surfaces could maintain sub-ambient temperatures under direct exposure to the sky and surroundings even when the solar intensity was 1000 W/m2 and downwelling atmospheric radiation was 480 W/m2, while separately achieving 2 °C below ambient during night-time with an effective cooling power of 54.4 W/m2. With a scalable fabrication-process, our cost-effective single-layer coating can be easily applied to diverse substrates, which is suitable for real-world applications in the tropics. Ministry of Education (MOE) Published version This study was funded by the Singapore Ministry of Education through grant no. 2018-T1-001-070.