Heterogenous electrocatalysts based on transition metal sulfides (TMS) are being actively explored in renewable energy research because nanostructured forms support high intrinsic activities for both the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). In this review article, the authors describe how researchers are working to improve the This article is protected by copyright. All rights reserved. 2 performance of TMS-based materials by manipulating its internal and external nanoarchitectures. A general introduction to the water splitting reaction is initially provided to explain the most important parameters in accessing the catalytic performance of nanomaterials catalysts. Later, the general synthetic methods used to prepare TMS-based materials is explained in order to delve into the various strategies being used to achieve higher electrocatalytic performance in HER. Complementary strategies can be used to increase the OER performance of TMS, resulting in bifunctional water-splitting electrocatalysts for both HER and OER. Finally, the current challenges and future opportunities of TMS materials in the context of water splitting are summarized. The authors aim to provide insights gathered in the process of studying TMS, and describe valuable guidelines for engineering other kinds of nanomaterial catalysts for energy conversion and storage technologies.

Highly conductive PEDOT films were prepared by solution casting polymerization using finely tuned oxidation solution and used as electrodes for the precise control of the oxidation level of the polymer electrochemically. They exhibited a large power factor of 1,270 mW m À1 K À2 and could be processed as flexible and cuttable thermoelectric films to generate electricity by fingertips.

Electrochromism, photothermal effect, and thermoelectric properties of hexyl-derivatized poly(3,4-ethylenedioxyselenophene) are investigated by precisely controlling the morphology. These properties are clearly demonstrated by controlling the applied electrical potential of the polymer films. Especially, the doped polymer film at -0.1 V reveals the highest photothermal conversion efficiency and a power factor of 42.5% and 354.7 μW m(-1) K(-2) , respectively. Efficient visible to near-infrared absorption, photon to heat, and heat to electric conversion has been realized in one film that could benefit in exploiting multifunctional film displays, invisible NIR sensors, photodynamic theragnosis, and thermoelectric devices.

Herein, the synergistic effects of hollow nanoarchitecture and high specific surface area of hollow activated carbons (HACs) are reported with the superior supercapacitor (SC) and capacitive deionization (CDI) performance. The center of zeolite imidazolate framework-8 (ZIF-8) is selectively etched to create a hollow cavity as a macropore, and the resulting hollow ZIF-8 (HZIF-8) is carbonized to obtain hollow carbon (HC). The distribution of nanopores is, subsequently, optimized by KOH activation to create more nanopores and significantly increase specific surface area. Indeed, as-prepared hollow activated carbons (HACs) show significant improvement not only in the maximum specific capacitance and desalination capacity but also capacitance retention and mean desalination rates in SC and CDI, respectively. As a result, it is confirmed that well-designed nanoarchitecture and porosity are required to allow efficient diffusion and maximum electrosorption of electrolyte ions.

Conductivity‐controllable and photo‐patternable conductive polythiophenes are prepared by solution‐casting polymerization and applied to patterned electrochromic devices. A photofunctional group is introduced to thiophene derivatives for color tuning. This method and the resulting materials support the easy fabrication of electrochromic devices for large smart windows or flexible displays with designability and processability.