Safe and sustainable energy storage systems with the ability to perform efficiently during large numbers of charge/discharge cycles with minimum degradation define the main objective of near future energy storage technologies. Closing the gap between high power and energy per unit weight requires new materials that can act as a battery and capacitor at the same time. Conductive polymers have attracted attention as hybrid battery-capacitor materials. However, their potential impact has not been fully investigated because their behaviour, especially in non-aqueous electrolytes such as ionic liquids, is not completely understood. Here, we aim to clarify the fundamental functionality of these hybrid characteristics while studying the interaction between a conductive polymer and an ionic liquid by in situ atomic force microscopy and electrochemical quartz crystal microbalance. The main achievement is the visualisation of the morphological modifications of the conductive polymer depending on the state of charge. These modifications significantly influence the viscoelastic material properties of the polymer. Our combined findings provide a model which explains why conductive polymers behave like (pseudo)-capacitors at a high state of charge and as batteries at a low state of charge. This understanding enables application-orientated synthesis of conductive polymers and their use as high-performance energy storage materials.

Nanoporous CuO layer on Cu foil with a thick Cu2O interlayer is synthesized via post annealing of previously fabricated Cu(OH)2 nanowires at 500 °C under an oxygen flow. The formation of the thick sandwiched Cu2O layer is realized through the outward diffusion of Cu ions and subsequent oxidation. An O2 pressure above the dissociation pressure of CuO is used to form a CuO layer at the outer surface of the structure, thus realizing a low cost structure having a porous and high isoelectric point layer. The Cu/Cu2O/CuO structure is used as an efficient electrode for glucose sensing. Sensitivities of [Formula: see text] at 0.8 V versus Ag/AgCl and 1066 μA mM(-1) cm(-2) at 0.6 V versus Ag/AgCl are achieved in an enzymatic and non-enzymatic glucose sensing schemes, respectively. The improved electrochemical sensing ability might be attributed to the efficient electrocatalytic reaction on the high crystal quality CuO layer and the porous structure.

Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar‐driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge‐based design rules, and scalable engineering strategies. Herein, competitive artificial leaf devices for water splitting, focusing on multiabsorber structures to achieve solar‐to‐hydrogen conversion efficiencies exceeding 15%, are discussed. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10–20 mA cm⁻² must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so‐called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Herein, corresponding research efforts to produce green hydrogen with unassisted solar‐driven (photo‐)electrochemical devices are discussed and reported.