The proton-exchange membrane fuel cell (PEMFC) is the most promising fuel cell technology because of the high power density and fast start-up. However, PEMFCs have not yet been commercialized on a large scale due to many technical problems. One of the key challenges for optimum fuel cell performance is maintaining the PEMFC at a proper temperature. This paper proposes a temperature fuzzy control strategy to adjust the stack temperature. A mathematical model of the cooling circuit was established to facilitate the control design. Then a kind of improved quantum particle swarm optimization (IQPSO) was introduced to optimize fuzzy control rules. The established model and fuzzy controllers were simulated and analyzed. The results of proportional integral derivative (PID) control, fuzzy-PID control (FPID), and fuzzy-PID control method with IQPSO algorithm (IQPSO-FPID) were compared. Simulation results showed that the IQPSO-FPID can meet many control objectives and improve control performance.

The effects of different configurations of a metal foam flow field on current density and temperature gradient of a single channel solid oxide fuel cell (SOFC) are investigated, and the overall performance of the optimum configuration is optimized. First, model A (conventional channel-rib flow field) is compared with three different configurations (i.e., model B with metal foam flow field only at anode, model C with that only at cathode, and model D at both). Although model C achieves the highest current density, its temperature is also fairly high. Although model B achieves the lowest temperature gradient, its current density is also fairly low. Model D performs well in both current density and temperature gradient. Then, the effect of electrode thickness and metal foam thickness on the performance of model D is investigated. The Ohmic polarization of model D remains almost constant with different electrode thicknesses, and its concentration polarization decreases as the electrode thickness decreases, which is totally different from the channel-rib flow field. Moreover, a thinner cathode causes lower activation overpotential, whereas a thinner anode causes higher activation overpotential. In general, a thick anode, a thin cathode, and thin metal foam can maximize the current density of model D, while a thick electrode and metal foam can always reduce the temperature gradient. Finally, the Taguchi method and gray relational analysis are used to optimize the current density and temperature gradient of model D. The current density of an optimized model is 3.27% higher than that of the original model with a temperature gradient of 9.05 K/cm.

In this study, a three-dimensional direct ammonia solid oxide fuel cell (DA-SOFC) was numerically modeled to investigate the effects of ammonia inlet flow velocity, tube structure, and catalyst filling on the internal temperature distribution of the cell. The results show that shortening the length of the ammonia inlet tube and increasing the inlet flow velocity leads to an increase in the temperature difference inside the cell. By perforating the ammonia inlet tube, the temperature difference can be further reduced, and the low-temperature zone inside the cell gradually decreases with the perforated area percentage increasing. In addition, placing ammonia decomposition catalyst inside the perforated inlet tube can further improve the temperature difference between the electrodes inside the cell, reducing it from 30 K to about 1 K. Furthermore, the temperature distribution pattern inside the fuel cell with metal supports was investigated, and it was found that the metal support can better export the heat generated inside the fuel cell. This study provides a new idea to improve the temperature distribution of DA-SOFC and enhance the stability and reliability of cell operation.

Electrocatalytic nitrate reduction to ammonia (NITRR) provides a sustainable avenue for simultaneous nitrate mitigation and ammonia synthesis, but the sluggish surface hydrogen migration during NITRR remains a major bottleneck. Here, we show a barrierless hydrogen transfer pathway along intramolecular hydrogen bonds between hydroxyls of hydroxyl-rich nanocavities for efficient nitrate electroreduction to ammonia. This nanocavity is constructed via electrochemical reduction-assisted selective Sr ions leaching on the La _0.4 Sr _0.6 FeO _3-δ perovskites. Combined experimental and theoretical investigations reveal that the nanocavity features nanocavity-like architecture with hydroxyl-enriched walls, boosting active hydrogen generating and hopping for NO ₃ ^- hydrogenation. Benefiting from such unusual intramolecular hydrogen transfer, the surface nanoconcaved La _0.4 Sr _0.6 FeO _3-δ achieves a Faradaic efficiency of 97.81 % and an ammonia yield rate of 51.37 mg h ⁻¹ cm ⁻² at −0.8 V versus reversible hydrogen electrode (RHE), surpassing nanocavity-free counterpart and ranking among superior NITRR catalysts. Ampere-level current density of nitrate-to-ammonia conversion are further realized in a renewable-energy-powered electrolyzer at a very low cell voltage of 2.23 V. Techno-economic analysis underscores dual benefits of this process including economic viability in ammonia synthesis and environmental impact in nitrate remediation.