Fired brick is a universal building material, produced by thousand-year-old technology, that throughout history has seldom served any other purpose. Here, we develop a scalable, costeffective and versatile chemical synthesis using a fired brick to control oxidative radical polymerization and deposition of a nanofibrillar coating of the conducting polymer poly(3,4ethylenedioxythiophene) (PEDOT). A fired brick's open microstructure, mechanical robustness and~8 wt% α-Fe 2 O 3 content afford an ideal substrate for developing electrochemical PEDOT electrodes and stationary supercapacitors that readily stack into modules. Fiveminute epoxy serves as a waterproof case enabling the operation of our supercapacitors while submerged underwater and a gel electrolyte extends cycling stability to 10,000 cycles with~90% capacitance retention.

Iron corrosion, a product from the chemical reaction between iron and oxygen in the presence of water and commonly referred to as rust, is a heterogeneous solid-state material composed of multiple phases that represent an abundant source of chemical waste. Here, we introduce a strategy that advances the state-of-the-art in chemical synthesis by demonstrating the usefulness of this ubiquitous inexpensive inorganic material for developing oxidative radical polymerizations. Rust, when treated with an acid, is an ideal source of Fe3+ ions affording an oxidation potential of 0.77 V for oxidizing thiophene-based moieties and producing conducting polymers characterized by long conjugation lengths. We develop fundamental knowledge and mechanistic understanding that enables the deposition of freestanding nanofibrillar films of the conducting polymer poly­(3,4-ethylenedioxythiophene) (PEDOT) via rust-based vapor-phase polymerization (RVPP). Our process takes place in a single step inside a sealed hydrothermal reactor when monomer vapor makes contact with a solid-state rust coating undergoing dissolutionthis approach is scalable requiring only a rusted steel surface, acid vapor, and monomer vapor. Freestanding nanofibrillar PEDOT films delaminate from a steel substrate characterized by an electronic conductivity of 323 S cm–1 and high electrochemical stability; RVPP enables patterning of a film in situ during synthesis. RVPP–PEDOT films are engineered into supercapacitors resulting in devices that exhibit a state-of-the-art capacitance of 181 F g–1 at a current density of 3.5 A g–1 and retain 80% of their original capacitance after 38 000 cycles.

We introduce a novel condensing vapor phase polymerization (CVPP) strategy for depositing microtubes of the conducting polymer polypyrrole; these serve as one-dimensional hollow microstructures for storing electrochemical energy. In CVPP, water droplets are structure-directing templates for polypyrrole microtubes. Water vapor condensation and polymerization occur simultaneously-conformal coatings of microtubes deposit on porous substrates such as hard carbon fiber paper or glass fiber filter paper. A mechanistic evolution of the microtubular morphology is proposed and tested based on the mass transport of water and monomer vapors as well as on the reaction stoichiometry. A coating of PPy microtubes is characterized by a high reversible capacitance of 342 F g at 5 mV s throughout 5000 cycles of cyclic voltammetry and a low sheet resistance of 70.2 Ω □. The open tubular structure is controlled in situ during synthesis and leads to electrodes that exhibit electrochemical stability at high scanning rates up to 250 mV s retaining all stored charge, even after extensive cycling at 25 mV s.

The diversity of nanostructures obtained from organic polymerization is limited when compared to the huge amount of documented inorganic nanostructures. In this paper, we elucidate a synergistic mechanism between in situ inorganic salt hydrolysis and vapor-phase polymerization for the metal oxide-poly­(3,4-ethylenedioxythiophene) (PEDOT) hybrid nanostructure growth. The steady state polymer growth and kinetically controlled hydrolysis enables homogeneous deposition of high-aspect-ratio crystal phases such as β-FeOOH, TeO2, and SnO2 coated by a conducting polymer. By controlling the hydrolysis kinetics, the hybrid material is synthesized in one step with morphologies controlled from 1D nanofibers to 2D nanoflowers and nanostructures from monolithic to core–shell. This fundamental understanding of the connection between hydrolysis and polymerization allows the future development of nanostructured inorganic, polymeric, and inorganic–organic hybrid materials. Enabled by this study, electrodes for energy storage are fabricated with different PEDOT morphologies, and their structure–property relationships are discussed. The 1D fibrillar structure shows a higher capacitance of 185 F/g at 25 mV/s compared to 2D nanoflowers because this morphology enhances electrolyte diffusion kinetics that facilitate PEDOT doping and dedoping, leading to a lower internal resistance.

Horizontally directed nanofibrillar PEDOT mats bearing high impact energy densities are fabricated as electrodes for impact-resistant flexible supercapacitors.