Can structure influence hydrovoltaic energy generation? Insights from the metallic 1T' and semiconducting 2H phases of MoS$_2$

TL;DR

This study compares metallic 1T' and semiconducting 2H phases of MoS₂ to understand how their structural differences affect hydrovoltaic energy generation, revealing phase-dependent performance and underlying mechanisms.

Contribution

It demonstrates how phase engineering of MoS₂ influences hydrovoltaic power output, highlighting the importance of material structure and properties for optimizing energy generation.

Findings

1T' phase achieves higher power density than 2H phase.

Hydrophilicity and interlayer channels are critical for performance.

Energy generation mainly from electro-kinetic and surface diffusion mechanisms.

Abstract

Hydrovoltaic power generation from liquid water and ambient moisture has attracted considerable research efforts. However, there is still limited consensus on the optimal material properties required to maximize the power output. Here, we used laminates of two different phases of layered MoS$_2$ -- metallic 1T' and semiconducting 2H -- as representative systems to investigate the critical influence of specific characteristics, such as hydrophilicity, interlayer channels, and structure, on the hydrovoltaic performance. The metallic 1T' phase was synthesized via a chemical exfoliation process and assembled into laminates, which can then be converted to the semiconducting 2H phase by thermal annealing. Under liquid water conditions, the 1T' laminates, having a channel size of 6 angstroms, achieved a peak power density of 2.0 mW m$^{-2}$, significantly outperforming the 2H phase, lacking defined channels, that produced a power of 2.4 microW m$^{-2}$. Our theoretical analysis suggests that energy generation in these hydrophilic materials primarily arises from electro-kinetic and surface diffusion mechanisms. These findings highlight the crucial role of phase-engineered MoS$_2$ and underscore the potential of 2D material laminates in advancing hydrovoltaic energy technologies.