Coconut shells, low-cost and renewable agro-wastes, were used as a starting material in the synthesis of hierarchical activated carbons via hydrothermal, KOH-activation, and carbonization techniques. The ratio of KOH to hydrochar was varied in a systemic manner to study how it influences the texture and electrochemical behavior of the capacitor. Coconut shell-based carbon coated on nickel foams presented a surface area of 1567 m² g⁻¹, with micropores as well as mesopores widely distributed. The sample showed superior electrochemical performance, attaining 449 F g⁻¹ at 1 A g⁻¹ in 6 M LiNO₃ aqueous solution. The solid-state symmetric supercapacitor device delivered a specific capacitance of 88 F g⁻¹ at 1 A g⁻¹ and a high energy density of 48.9 Whkg⁻¹ at a power density of 1 kW kg⁻¹. At a wide voltage window of 2.0 V, the sample was highly stable during the cycle test, showing a 92% capacitance retention at 2 A g⁻¹ after cycling for 5000 times. The superior performance is due to the sample possessing great BET surface area, a good distribution of pores, and the usage of a suitable electrolyte. This facilitates an electrical double layer that can be deployed for applications to store energy.

The rapid emergence of Industry 4.0 implies that our engineering graduates need to acquire new competences to adapt to the digital transformation. This paper evaluates the benefits of integrating 3D printing and Industry 4.0 into engineering undergraduate programs. Surveys were conducted to gather the feedbacks and views from academics and students. 75% and 86% of the participating students and lecturers, respectively, have heard about Industry 4.0. 63% of the students were exposed to modules with such elements. Tangible 3D-printed models enable visualization of fundamental theories and concepts. Enhanced 3D drawing skills and rapid 3D-printed prototypes can greatly help students study common processing equipment, manufacturing, maintenance, logistics, and operations. Some limitations were identified such as budgeting, lack of knowledge, and difficulty in changing from traditional pedagogy. This paper thus proposes a blended learning model for integrating Industry 4.0 into engineering teaching, which consists of traditional, online learning, and flipped classroom approaches. Implementation of the model can be started off with cross-multidisciplinary collaborations or expert-led training for the instructors, followed by traditional face-to-face teaching and online learning. Flipped classroom is one of the essential components of the model which encourages learning-by-making approaches such as ‘bring your own device’ and ‘do it yourself’. Integrating Industry 4.0 into engineering teaching can create a student-based learning environment, where students are gradually trained to become proactive and lifelong learners who are more conscious of the environment and economy.

Microbial fuel cell (MFC) technology has attracted a great amount of attention due to its potential for organic and inorganic waste treatment concomitant with power generation. It is thus seen as a clean energy alternative. Modifications and innovations have been conducted on standalone and hybrid/coupled MFC systems to improve the power output to meet the end goal, namely, commercialization and implementation into existing wastewater treatment plants. As the energy generated is inversely proportional to the size of the reactor, the stacking method has been proven to boost the power output from MFC. In recent years, stacked or scale-up MFCs have also been used as a power source to provide off-grid energy, as well as for in situ assessments. These scale-up studies, however, encountered various challenges, such as cell voltage reversal. This review paper explores recent scale-up studies, identifies trends and challenges, and provides a framework for current and future research.

Three kinds of MnO₂/Ni foam composite electrode with hierarchical meso-macroporous structures were prepared using potentiodynamic (PD), potentiostatic (PS), and a combination of PS and PD(PS + PD) modes of electrodeposition. The electrodeposition mode markedly influenced the surface morphological, textural, and supercapacitive properties of the MnO₂/Ni electrodes. The supercapacitive performance of the MnO₂/Ni electrode obtained via PS + PD(PS + PD(MnO₂/Ni)) was found to be superior to those of MnO₂/Ni electrodes obtained via PD and PS, respectively. Moreover, an asymmetric supercapacitor device, activated carbon (AC)/PS + PD(MnO₂/Ni), utilizing PS + PD(MnO₂/Ni) as a positive electrode and AC as a negative electrode, was fabricated. The device exhibited an energy density of 7.7 Wh·kg⁻¹ at a power density of 600 W·kg⁻¹ and superior cycling stability, retaining 98% of its initial capacity after 10,000 cycles. The good supercapacitive performance and excellent stability of the AC/PS + PD(MnO₂/Ni) device can be ascribed to its high surface area, hierarchical structure, and interconnected three-dimensional reticular configuration of the nickel metal support, which facilitates electrolyte ion intercalation and deintercalation at the electrode/electrolyte interface and mitigates volume change during repeated charge/discharge cycling. These results demonstrate the great potential of the combination of PS and PD modes for MnO₂ electrodeposition for the development of high-performance electrodes for supercapacitors.

A series of heteroatom-containing porous carbons with high surface area and hierarchical porosity were successfully prepared by hydrothermal, chemical activation, and carbonization processes from soybean residues. The initial concentration of soybean residues has a significant impact on the textural and surface functional properties of the obtained biomass-derived porous carbons (BDPCs). SRAC5 sample with a BET surface area of 1945 m² g⁻¹ and a wide micro/mesopore size distribution, nitrogen content of 3.8 at %, and oxygen content of 15.8 at % presents the best electrochemical performance, reaching 489 F g⁻¹ at 1 A g⁻¹ in 6 M LiNO₃ aqueous solution. A solid-state symmetric supercapacitor (SSC) device delivers a specific capacitance of 123 F g⁻¹ at 1 A g⁻¹ and a high energy density of 68.2 Wh kg⁻¹ at a power density of 1 kW kg⁻¹ with a wide voltage window of 2.0 V and maintains good cycling stability of 89.9% capacitance retention at 2A g⁻¹ (over 5000 cycles). The outstanding electrochemical performances are ascribed to the synergistic effects of the high specific surface area, appropriate pore distribution, favorable heteroatom functional groups, and suitable electrolyte, which facilitates electrical double-layer and pseudocapacitive mechanisms for power and energy storage, respectively.