A High Efficiency Osmotic Energy Harvester with Vertically Aligned Boron-Nitride-Nanopore Membrane

Abstract

Application of the abundant salinity-gradients in the environment, motivated by the Gibbs free energy of mixing fresh and salt water, has been under intensive investigation for clean-energy harvesting. Globally, there is a potential of at least 2.6 TW of power that could be generated at coastal estuaries from the ion-concentration gradient. Recent investigation on an energy conversion efficiency of single boron nitride nanotube (BNNT) has revealed the huge potential of an efficient exploitation of electrokinetic phenomena in nanofluidic systems for energy harvesting. Here, for the first time, we demonstrate rationally designed nanostructured vertically aligned boron-nitride-nanopore membranes (VA-BNNP) which can efficiently harness osmotic power from salinity gradient. A thin hexagonal boron nitride (hBN) layer was uniformly deposited within the pores of anodized alumina substrates by low-pressure chemical vapor deposition which produced first-ever macroscopic VA-BNNP membrane with high nanopore density, up to ~108 pores/cm2. Cross-sectional scanning-electron-microscope (SEM) images show the hBN layer (~35 nm) was uniformly deposited along the pores without excessive hBN on the top surface, ensuring that most pores remained open. In addition, the results of scanning confocal Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) showed the high quality of the hBN layers in the AAO pores. We investigated the power generation of the macroscopic VA-BNNP membranes at different pH and salinity concentrations. The power generation per unit pore area increased as the salt concentration and pH increased. The highest power density of the membrane was up to ~100 W/m2 which is two orders of magnitude higher than that of other macro-scale, salinity gradient driven, power generation system reported so far. In addition, we also elucidate the fundamental ion transport mechanism in BN nanopore using the molecular dynamic simulations to support to the experimental power density values. These findings indicate the great potential of large-area VA-BNNP membranes as next-generation nanostructured membranes for renewable energy harvesting.

Experimental and Theoretical Insights into Interfacial Properties of 2D Materials for Selective Water Transport Membranes: A Critical Review

“…81−85 Its applications span various areas, including separation technologies, 6,86,87 nanofluidic systems, 88 and osmotic power harvesting. 89,90 In a preliminary investigation, Allendorf and coresearchers explored the kinetics of boron nitride (BN) gas-phase CVD employing BCl 3 and NH 3 precursors. 91 The outcomes of their study unveiled the significance of Cl 2 BNH 2 , an intermediate compound generated in the course of the reaction between BCl 3 and NH 3 , in facilitating the CVD growth of BN.…”

“…hBN is a 2D inorganic material with insulating properties, commonly referred to as white graphene . It has also attracted considerable interest due to its exceptional properties, including high mechanical strength. − Its applications span various areas, including separation technologies, ,, nanofluidic systems, and osmotic power harvesting. , In a preliminary investigation, Allendorf and coresearchers explored the kinetics of boron nitride (BN) gas-phase CVD employing BCl 3 and NH 3 precursors . The outcomes of their study unveiled the significance of Cl 2 BNH 2 , an intermediate compound generated in the course of the reaction between BCl 3 and NH 3 , in facilitating the CVD growth of BN.…”

Chemical vapor deposition of 2D materials: A review of modeling, simulation, and machine learning studies

“…Hexagonal boron nitride (hBN), also known as white graphene, is an insulating 2D material that has found application in several areas, such as optoelectronic devices ( Caldwell et al., 2019 ; Cheng et al., 2019 ; Ougazzaden et al., 2021 ), molecular/ionic separations ( Gao et al., 2017 ; Lei et al., 2013 ), and osmotic power harvesting ( Kim et al., 2019 ; Macha et al., 2019 ; Yazda et al., 2021 ). An early work by Allendorf and group investigated the kinetics of the gas-phase CVD growth of boron nitride (BN) from BCl 3 and NH 3 precursors.…”