Energy-conversion devices based on the phenomenon of proton conduction, for example, polymer electrolyte membrane fuel cells (PEMFCs), require low cost and sustainable electrolytes with high ionic conductivity and good mechanical properties under anhydrous conditions and at temperatures up to 150 °C. Biopolymers possess an intrinsic thermomechanical stability but an insufficient proton conductivity in the dry state, which however may be imparted by a protic ionic liquid (PIL). This work presents the preparation and properties of composite membranes made of cellulose nanocrystals (CNCs) and a PIL. The membranes are thermally stable and display an ionic conductivity within the range 10-4-10-3 S/cm for temperatures between 120 and 160 °C. Moreover, the analysis of the biopolymer's apparent dimensions at nanoscale reveals a dependence of the CNCs' defects, twisting, and aggregation in the presence of the PIL. Preliminary tests using a simple fuel cell setup demonstrate a response of the membranes to the inlet of H2 gas, with a generation of electrical current. These findings provide a solid groundwork for further development and future studies of biopolymer/PIL electrolytes for energy applications. © 2021 The Authors.

Corrosion resistance and catalytic activity toward the oxygen reduction reaction (ORR) in an alkaline environment are two key properties for water recombination applications. In this work, CoCrFexNi (0 ≤ x ≤ 0.7) thin films were deposited by magnetron sputtering on polished steel substrates. The native passive layer was 2-4 nm thick and coherent to the columnar grains determined by transmission electron microscopy. The effect of Fe on the corrosion properties in 0.1 M NaCl and 1 M KOH and the catalytic activity of the films toward ORR were investigated. Electrochemical impedance spectroscopy and potentiodynamic polarization measurements indicate that CoCrFe0.7Ni and CoCrFe0.3Ni have the highest corrosion resistance of the studied films in NaCl and KOH, respectively. The high corrosion resistance of the CoCrFe0.7Ni film in NaCl was attributed to the smaller overall grain size, which leads to a more homogeneous film with a stronger passive layer. For CoCrFe0.3Ni in KOH, it was attributed to a lower Fe dissolution into the electrolyte and the build-up of a thick and protective hydroxide layer. Scanning Kelvin probe force microscopy showed no potential differences globally in any of the films, but locally, a potential gradient between the top of the columns and grain boundaries was observed. Corrosion of the films was likely initiated at the top of the columns where the potential was lowest. It was concluded that Fe is essential for the electrochemical activation of the surfaces and the catalytic activity toward ORR in an alkaline medium. The highest catalytic activity was recorded for high Fe-content films (x ≥ 0.5) and was attributed to the formation of platelet-like oxide particles on the film surface upon anodization. The study showed that the combination of corrosion resistance and catalytic activity toward ORR is possible for CoCrFexNi, making this material system a suitable candidate for water recombination in an alkaline environment. 

Currently, there is a strong need to accelerate development of systematic and robotized procedures for discovery of photovoltaic materials in order to aid the transition toward the use of clean and sustainable energy sources. Perovskite-type materials represent a broad class of compounds that have recently attracted great interest for application as photovoltaic materials. Such materials offer a vast chemical and structural space, qualifying them as an interesting starting point for further exploration using robotized screening methods. In this work, the development and application of a robotized procedure for the screening and solar cell characterization of perovskite-inspired materials is presented. Several combinations of cationic dyes and metal halides were examined by using a fully automated robotic screening cycle, including solar cell characterization based on triple mesoscopic solar cell devices. It is shown that the presented methodology is promising for the detection of new photovoltaic materials, which is demonstrated by the discovery of a selection of photovoltaic candidates. Some of the discovered candidates, for instance [QR][PbI3], were further characterized theoretically and experimentally. 

Two new organic–inorganic hybrid perovskite compounds, (Me₃S)₂Pb₅I₁₄*2I₂ (1) and (C₈H₁₁S)₂Pb₂I₆*I₂ (2), have been synthesized and subsequently characterized in this study. The materials were synthesized from facile one-pot, one-step reactions of lead iodide, corresponding sulfide, methanol, iodine, and hydroiodic acid in the case of 2. Structural analysis reveals the presence of polyiodide entities in both compounds. Compound 1 contains triiodide anions, I₃^–, that are uniquely shared between the 2D inorganic slabs, forming a 3D network. Both 1 and 2 have I₂ molecules that are bridging the inorganic slabs through a structural motif that can be regarded as a tetraiodide anion, I₄^2–. Optical spectroscopy shows band gaps of 1.86 eV for 1 and 1.89 eV for 2. The optoelectronic properties were further investigated with band structure calculations. Single-crystal IV-characteristics of 1 show that the compound is photoactive confirming it as a promising photovoltaic candidate. Compound 1 highlights a novel strategy of designing 3D semiconducting hybrid materials by incorporating polyiodides to provide direct geometric and electronic connections between the semiconducting inorganic perovskite sheets.

We demonstrated an asymmetric aqueous supercapacitor made of p- and n-type conducting polymer electrodes. We used the high electron affinity (EA) n-type polymer poly(benzimidazobenzophenanthroline) (BBL) as the anode conducting material, and the low ionization potential (IP) p-type polar polythiophene p(g42T-T) as the cathode material. EABBL matches IPp(g42T-T), enabling the fabrication of all-organic asymmetric p/n-supercapacitors that function in aqueous electrolytes. The devices operate in a voltage window up to 1 V, yielding areal capacitances of 90 mF cm-2 and specific capacitances of 33 F g-1 as well as excellent cycling stability with almost 100% capacitance retention over 10 000 cycles.