3D printing technology provides a unique platform for rapid prototyping of numerous applications due to its ability to produce low cost 3D printed platforms. Herein, a graphene-based polylactic acid filament (graphene/PLA) has been 3D printed to fabricate a range of 3D disc electrode (3DE) configurations using a conventional RepRap fused deposition moulding (FDM) 3D printer, which requires no further modification/ex-situ curing step. To provide proof-of-concept, these 3D printed electrode architectures are characterised both electrochemically and physicochemically and are advantageously applied as freestanding anodes within Li-ion batteries and as solid-state supercapacitors. These freestanding anodes neglect the requirement for a current collector, thus offering a simplistic and cheaper alternative to traditional Li-ion based setups. Additionally, the ability of these devices’ to electrochemically produce hydrogen via the hydrogen evolution reaction (HER) as an alternative to currently utilised platinum based electrodes (with in electrolysers) is also performed. The 3DE demonstrates an unexpectedly high catalytic activity towards the HER (−0.46 V vs. SCE) upon the 1000th cycle, such potential is the closest observed to the desired value of platinum at (−0.25 V vs. SCE). We subsequently suggest that 3D printing of graphene-based conductive filaments allows for the simple fabrication of energy storage devices with bespoke and conceptual designs to be realised.

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Research into alternative renewable energy generation is a priority, due to the everincreasing concern of climate change. Microbial fuel cells (MFCs) are one potential avenue to be explored, as a partial solution towards combating the over-reliance on fossil fuel based electricity. Limitations have slowed the advancement of MFC development, including low power generation, expensive electrode materials and the inability to scale up MFCs to industrially relevant capacities. However, utilisation of new advanced electrode-materials (i.e. 2D nanomaterials), has promise to advance the field of electromicrobiology. New electrode materials coupled with a more thorough understanding of the mechanisms in which electrogenic bacteria partake in electron transfer could dramatically increase power outputs, potentially reaching the upper extremities of theoretical limits. Continued research into both the electrochemistry and microbiology is of paramount importance in order to achieve industrial-scale development of MFCs. This review gives an overview of the current field and knowledge in regards to MFCs and discusses the known mechanisms underpinning MFC technology, which allows bacteria to facilitate in electron transfer processes. This review focusses specifically on enhancing the performance of MFCs, with the key intrinsic factor currently limiting power output from MFCs being the rate of electron transfer to/from the anode; the use of advanced carbon-based materials as electrode surfaces is discussed.

Oxygen vacancies (OVs) dominate the physical and chemical properties of metal oxides, which play crucial roles in the various fields of applications. Density functional theory calculations show the introduction of OVs in TiO2(B) gives rise to better electrical conductivity and lower energy barrier of sodiation. Here, OVs evoked blue TiO2(B) (termed as B‐TiO2(B)) nanobelts are successfully designed upon the basis of electronically coupled conductive polymers to TiO2, which is confirmed by electron paramagnetic resonance and X‐ray photoelectron spectroscopy. The superiorities of OVs with the aid of carbon encapsulation lead to higher capacity (210.5 mAh g−1 (B‐TiO2(B)) vs 102.7 mAh g−1 (W‐TiO2(B)) at 0.5 C) and remarkable long‐term cyclability (the retention of 94.4% at a high rate of 10 C after 5000 times). In situ X‐ray diffractometer analysis spectra also confirm that an enlarged interlayer spacing stimulated by OVs is beneficial to accommodate insertion and removal of sodium ions to accelerate storage kinetics and preserve its original crystal structure. The work highlights that injecting OVs into metal oxides along with carbon coating is an effective strategy for improving capacity and cyclability performances in other metal oxide based electrochemical energy systems.

The electrochemistry of microdroplets, shown to be nearly monodisperse, of N,N,N‘,N‘-tetraalkyl-para-phenylenediamine oils (TRPD, R = n-butyl, n-hexyl, n-heptyl, and n-nonyl) immobilized on a basal plane pyrolytic graphite electrode and immersed into aqueous electrolyte solution is studied using cyclic voltammetry. Upon oxidation of the TRPD droplet to the cation radical TRPD+•, anion uptake from, or cation loss into the aqueous solution takes place, so as to maintain electroneutrality within the oily deposit. The former process is shown to produce an ionic liquid, with the anion insertion taking place at the triple phase boundary of electrode |TRPD oil| aqueous electrolyte; the latter process, in contrast, takes place at the interface between the two immiscible liquids, and with two-thirds-order kinetics. The possibility of a chemical reaction taking place between the electrogenerated and inserted ions at the three-phase junction, viz. redox-catalysis or otherwise, is illustrated via reference to two systems (azide and iodide).

Mostly reported MoSe2 suffered from easily stacking problem, volume expansion and relative low capacity. From the experience of Li/Na-Se batteries, the exfoliated and encapsulated MoSe2 inside carbon nanospheres with C-O-Mo bonds and large layer distance (0.89 nm) are successfully constructed. This unique effective structure has C-O-Mo bonding allowing high conductivity across the Se-O insulation layer and promoting its reversible conversion. The first-principles calculations demonstrated that the frontier molecular orbitals of C-O-Mo interface structure are mainly localized on the MoSe2 sheet fragment with an appropriate HOMO-LUMO gap (< 4eV),suggesting its good stability and conductivity. Utilized as anodes for LIBs allows a Li-storage capacity to be realized of 1208 mAh g -1 after 150 cycles at 1.0 A g -1 and 519 mAh g -1 after 200 cycles at 4.0 A g -1 . The Na-storage capacity is found to be 543, 491 mAh g -1 after 120 cycles at 0.1, 1.0 A g -1 . Focusing on the analysis of CV, the reducing particle may improve the capacitive behaviors, further resulting the high-rate performance. Ex-situ techniques demonstrated that the emerging Se was constrained uniformly. The controlling of by-product Se plays a key role in achieving a high rate 2 capacity and cycling stability, and opens up a potential avenue for these metal-selenide anodes designs for battery storage systems.

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