Intrinsically Stretchable Fuel Cell Based on Enokitake‐Like Standing Gold Nanowires

Abstract

Depending on the scale involved, there are different challenges in contemporary energy research. At the large scale, the main challenge lies in the environmental issues involved in powering cities in a sustainable manner; at the medium scale, the main challenge lies at simultaneously high energy and power density to drive electrical vehicles; at the small scale, the main challenge is how to power wearable and implantable devices anytime and anywhere without the need of external power supply of bulky connecting wires. To realize this latter goal, energy conversion/storage devices need to be ultrathin yet highly functional when being bent, twisted, and stretched. [1][2][3][4][5] However, current energy devices remain bulky and rigid. Despite the development of commercial paper batteries, these devices are not stretchable. [6,7] Therefore, it is highly desirable to develop thinner, softer, more biocompatible, and skin-conformal energy technologies to power future medical devices.It is encouraging to witness recent growing interest in stretchable devices including battery, [8,9] photovoltaics, [10,11] triboelectric generator, [12,13] supercapacitor, [14,15] and fuel cells. [16,17] To date, some biofuel cell based stretchable energy devices have been developed to power wearable electronic devices. [16][17][18][19] Nevertheless, their performance depends largely on the enzyme or bacteria, [16,[19][20][21] and their activity is affected by many factors, including the temperature and pH. [22,23] In contrast, methanol or ethanol based fuel cells have been shown to offer a much higher efficiency and reliability [24] because they are not influenced by external biological environments. To fabricate flexible fuel cells, specially designed electrodes or catalysts are required. In this context, carbon fiber paper or carbon cloth, [25,26] graphene paper, [27] and nickel foam [28] have been successfully utilized to fabricate flexible methanol or ethanol fuel cells. It is possible to design bendable on-chip fuel cells by imprinting Au on cycloolefin polymer films. [29] Ultralong Ag nanowires have been deposited onto polydimethylsiloxane (PDMS) forming percolation network, which can be used as current collectors for bendable fuel cells. [30] Despite the encouraging progress made so far, it remains highly challenging to fabricate stretchable fuel cells, which require new design of the electrodes and electro-catalysts. Conventional fuel cells are based on rigid electrodes, limiting their applications in wearable and implantable electronics.Here, it is demonstrated that enokitake-like vertically-aligned standing gold nanowires (v-AuNWs) can also serve as powerful platform for stretchable fuel cells by using ethanol as model system. Unlike traditional fuel cell electrodes, the v-AuNWs have "Janus Morphology" on both sides of the film and also are highly stretchable. The comparative studies demonstrate that tail side exposed v-AuNWs based stretchable electrodes outperform the head-side exposed v-AuNWs toward the electro-oxidation of eth...

Flourishing energy harvesters for future body sensor network: from single to multiple energy sources

“…Generally, the available energy sources around us include mechanical energy ( Liu et al, 2013 , 2014 ), solar energy ( Hashemi et al., 2020 ), thermal energy ( Xie et al., 2011 ; Zhang et al., 2019a ), and biochemical energy ( Jeerapan et al., 2020 ). As illustrated in Figure 1 B, there are various conversion mechanisms, including piezoelectric ( Shi et al., 2016a ; Sun et al., 2019a ), triboelectric ( Dong et al., 2021 ; Gunawardhana et al., 2020 ), and electromagnetic effects ( Zhang et al., 2020b ) for mechanical energy harvesting; the photovoltaic effect for solar energy harvesting ( Park et al., 2018 ); the thermoelectric or pyroelectric effect for thermal energy harvesting ( Sun et al., 2019c ; Yang et al., 2012 ); and biofuel cell for biochemical energy harvesting in biofluids ( Gong et al., 2020 ; Zhai et al., 2020 ). These renewable energy harvesters (EHs) have been attracting great attention and hold great promises to realize self-powered wireless sensor networks (WSN) for personal health care and smart home.…”

Engineering Single Atom Catalysts to Tune Properties for Electrochemical Reduction and Evolution Reactions

“…Fuel cell and battery‐based energy storage and conversion technologies strongly impact academic research and industrial initiatives. [ 1–6 ] Currently, more focus is directed towards storage technologies involving electric vehicles and power stations, [ 7–9 ] given their high efficiencies and low emissions. Hydrogen fuel cells, using renewable hydrogen gas for fuel and producing water as their sole byproduct, show significant potential as highly efficient devices for supplying clean energy, [ 10–12 ] especially for transportation.…”

Mechanically-gated electrochemical ionic channels with chemically modified vertically aligned gold nanowires

“…Recently, we have developed a wet chemistry approach to fabricate stretchable electrode by using the vertically aligned gold nanowires (v-AuNWs), which could serve as an unconventional electrochemical platform for soft wearable sensors for detecting strains ( Yap et al., 2019 ), pressures ( Wang et al., 2021 ), temperature ( Gong et al., 2019 ), and biological markers ( Zhai and Cheng, 2019 ; Zhai et al., 2019 , 2020a , 2020b ). Here, we further demonstrate a mechanically-gated electrochemical ionic channel based on chemically modified v-AuNWs with 1-Dodecanethiol (DDT) ( Figure 1 ).…”