Hydrogen production from thermochemical conversion has been considered the most promising technology for the use of biomass, and some novel methods are also being developed for low cost and high efficiency. This review presents the recent progress in the studies on hydrogen production from different kinds of biomass by pyrolysis, gasification and steam reforming without and/or with chemical-looping technologies. Considering potential applications, the Ni-based catalysts made of cheap and earth-abundant elements are especially important for the economically viable hydrogen production from biomass by thermochemical conversion, and can also effectively be compensated for and modified, to some extent, by using extremely low noble metal loading for retaining high catalytic activity, high coke resistance and long-term stability. The catalyst modification strategies of adding other metals, minimizing Ni particle sizes and improving the supports are highlighted. The sorption-enhanced steam reforming (SESR) and chemical looping steam reforming (SE-CLSR) processes with in situ CO₂ removal using different reactors have been considered to change the normal equilibrium limits of the water–gas shift (WGS) reaction, and thus increase feedstock conversion and process performances. The auto-thermal operating conditions and CO₂ capture during hydrogen production can be achieved by chemical looping processes with cyclic oxidation–reduction of oxygen carriers (OCs). This paper discusses the related issues, challenges and prospects, along with the possible solutions in order to help in the development of efficient hydrogen production from the thermochemical conversion of biomass.

In this study, a critical comparison between two low metal (Ni) loading catalysts is presented, namely Ni/Al₂O₃ and Ni/AlCeO₃ for the glycerol steam reforming (GSR) reaction. The surface and bulk properties of the catalysts were evaluated using a plethora of techniques, such as N₂ adsorption/desorption, Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP–AES), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy / Energy Dispersive X-Ray Spectroscopy (SEM/EDX, Transmission Electron Microscopy (TEM), CO₂ and NH₃– Temperature Programmed Desorption (TPD), and Temperature Programmed Reduction (H₂–TPR). Carbon deposited on the catalyst’s surfaces was probed using Temperature Programmed Oxidation (TPO), SEM, and TEM. It is demonstrated that Ce-modification of Al₂O₃ induces an increase of the surface basicity and Ni dispersion. These features lead to a higher conversion of glycerol to gaseous products (60% to 80%), particularly H₂ and CO₂, enhancement of WGS reaction, and a higher resistance to coke deposition. Allyl alcohol was found to be the main liquid product for the Ni/AlCeO₃ catalyst, the production of which ceases over 700 °C. It is also highly significant that the Ni/AlCeO₃ catalyst demonstrated stable values for H₂ yield (2.9–2.3) and selectivity (89–81%), in addition to CO₂ (75–67%) and CO (23–29%) selectivity during a (20 h) long time-on-stream study. Following the reaction, SEM/EDX and TEM analysis showed heavy coke deposition over the Ni/Al₂O₃ catalyst, whereas for the Ni/AlCeO₃ catalyst TPO studies showed the formation of more defective coke, the latter being more easily oxidized.

The heat storage technology can improve the performance of a solar thermal utilization system effectively. This work studied the effect of phase-change materials (PCMs) on thermal stratification in a heat storage tank. A 60 l sodium acetate trihydrate heat storage tank with 331.15 K phase-change temperature was designed and fabricated. A mathematical model was built to simulate the discharge process in the water tank, and the temperature distribution during the discharge process was obtained. The computational fluid dynamics model was verified by the experimental data. Furthermore, the Ri, the fill efficiency, and the MIX number were adopted to extensively analyze the performance of a heat storage tank with different positions of PCMs with the variation of flow rates. The results indicated that the distance between the isothermal surfaces of 303.15 K and 348.15 K in PCM1, PCM2, PCM3, and PCM4 were 11.75 cm, 11.13 cm, 10.52 cm, and 9.28 cm, respectively, with 9 l/min of flow velocity when t* = 0.7, showing that the thermal stratification was improved as the position of the PCMs got closer to the inlet. The PCMs’ half-life (the liquefaction rate reached 50%) was prolonged as the inlet flow rates increased. As the flow rate increased from 1 l/min to 5 l/min, the half-life of PCM4 delayed from a dimensionless time of 0.5 to a dimensionless time of 0.9. Moreover, when the flow velocity was 9 L/min, the liquefaction rate of PCM4 remained at 1. The calculated values of fill efficiency and Richardson number were higher than the experimental data slightly, while the MIX number was smaller than the experimental results. The experimental and calculated values of root mean square error (RMSE) increased with the increasing inlet flow velocity and the lowering of the positions of the PCMs.

The cryogenic supercritical hydrogen storage system offers notable advantages including heightened hydrogen storage density and operation under relatively moderate conditions compared to conventional hydrogen storage methodologies. In this study, a cryogenic supercritical hydrogen storage system based on the multi-stage Joule–Brayton refrigeration cycle is presented, analyzed, and optimized. The proposed system employs a five-stage cascade cycle, each stage utilizes a distinct refrigerant, including propane, ethylene, methane, and hydrogen, facilitated by Joule–Brayton cycles, with expanders employed for mechanical work recovery, which is capable of effectively cooling hydrogen from ambient temperature and atmospheric pressure to a cryogenic supercritical state of −223.15 °C (50 K), 18,000 kPa, exhibiting a density of 73.46 kg/m³ and a hydrogen processing capacity of 2 kg_H2/s. The genetic algorithm is applied to optimize 25 key parameters in the system, encompassing temperature, pressure, and flow rate, with the objective function is specific energy consumption. Consequently, the specific energy consumption of the system is 5.71 kWh/kg_H2 with an exergy efficiency of 56.2%. Comprehensive energy analysis, heat transfer analysis, and exergy analysis are conducted based on the optimized system parameters, yielding insights crucial for the development of medium- and large-scale supercritical hydrogen storage systems.

Hydrogen production from ethanol steam reforming (ESR) was performed using the synthesized LaNi_xCu_1−xO_3−λ perovskite-type catalysts in a continuous two-stage fixed-bed reactor from 450 to 700 °C under atmospheric pressure. The elemental analysis (EA), XRD, SEM, BET, and TGA-DTG technologies were used to characterize the structures and properties of the synthesized catalysts. The thermodynamic equilibrium model, based on the minimization of Gibbs free energy using a non-stoichiometric methodology, was carried out and compared with experimental data. The results demonstrated that the catalytic activity of the perovskite-type catalysts for ESR can be improved after modification with a certain amount of copper (about 0.67 mmol/g) and decreased further with an increase in copper content (about 3.41 mmol/g). The most active catalyst was found to be LaNi_0.9Cu_0.1O_3−λ, with an ethanol conversion value of 96.0% and hydrogen selectivity of 71.3%. The perovskite-type catalysts with an appropriate amount of Cu promoter improved coking resistance and presented excellent stability with no loss of activity over 101 h at 700 °C. Based on the power-law kinetic model with the first reaction order, the activation energy and the frequency factor for ethanol steam reforming by perovskite-type catalysts were calculated. Our studies indicated the enhanced effects of Ni and Cu on the small Ni-Cu bimetallic particles in the water gas shift (WGS) reaction, which could also contribute to the activity and stability of the LaNi_xCu_1−xO_3−λ perovskite-type catalysts in hydrogen production.