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Herein, a series of phosphorus-doped CoMoO4 rod bundles electrocatalysts on 3D nickel foams have been successfully synthesized and exploited as efficient hydrogen evolution reaction (HER) electrocatalyst in 1 M KOH. The incorporation of phosphorus into CoMoO4 can significantly promote the HER activity, and the CoMoO4 bundles phosphorized at 350 °C exhibited the optimum activity, which only required low overpotentials of 56 and 148 mV to deliver cathodic current densities of 10 mA cm−2 and 100 mA cm−2, respectively. This electrode also presented considerable long-term electrochemical stability with negligible delay after 30 h operation and 3000 accelerated cyclic voltammetry cycles. Our study provides a superior earth-abundant catalyst for efficient HER in alkaline media, which also suggests that P doping engineering is an effective way to boost the HER activity of transition metal-based oxides. [ABSTRACT FROM AUTHOR]

Herein, to develop ceramic foam filters (CFFs) with high porosity and strength, porous β-SiAlON ceramic foam was prepared using Si, α-Al 2 O 3 , and AlN via foam impregnation. Experiments were performed to investigate the effects of the slurry solid content, impregnation times, and sintering temperature on the sample properties. The best green bodies were obtained at a slurry solid content of ∼70 wt%, and the sample subjected to two impregnation times effectively filled the defects. The sintering temperature was found to affect the phase composition, microstructure, sintering behavior, mechanical properties, and oxidation resistance of β-SiAlON ceramic foams. Granular β-SiAlON started to develop at 1550 °C and was almost completely developed at 1600 °C. After sintering at 1650 °C, the porosity remained as high as 85.93% and the compressive strength reached 1.57 MPa. In a nonisothermal oxidation experiment, the maximum oxidation weight gain rate was 14.1% and the sample strength still reached 1.54 MPa at 1600 °C. A high sintering temperature promoted the development of material phases and liquefaction of grains, while the oxidized surface generated an amorphous layer with a high melting point, effectively preventing oxygen diffusion. Therefore, β-SiAlON can be employed to develop CFFs with high strength and excellent oxidation resistance. [ABSTRACT FROM AUTHOR]

Most phase change materials employed in latent heat thermal energy storage suffer from poor thermal conductivity both in liquid and solid phases, leading to low heat transfer effectiveness. To overcome this limitation, multiple PCMs and gradient copper foam have been used to accelerate the melting of phase change materials and improve the heat transfer effectiveness. The heat transfer performance of shell-and-tube thermal energy storage unit consisting of radial multiple PCMs and single PCM was numerically investigated. The utilization of single PCM showed better heat transfer effectiveness compared to that using radial multiple PCMs. The time saving for complete melting was up to 87.5%. The results implied that the radial multiple PCMs have no advantage in thermal storage compared to single PCM. Based on single PCM system, three types of gradients of copper foam, named positive gradient, non-gradient and negative gradient were designed in this study. The results indicated that the negative gradient type offers better heat transfer effectiveness than the non-gradient and positive gradient types. However, the temperature distribution of non-gradient type was more uniform compared to positive and negative types. Besides, an optimal configuration 0.99–0.97-0.89 of negative gradient was recommended to further reduce the complete melting time by 23.7%. • Melting performance of phase change materials in three types of copper foam was studied. • Single PCM showed better heat transfer compared to radial multiple PCMs. • The porosity gradient has a significant effect on the thermal performance. • The negative gradient type can provide better heat transfer effectiveness. •An optimal configuration 0.99–0.97-0.89 of negative gradient was recommended. [ABSTRACT FROM AUTHOR]

Developing efficient oxygen evolution reaction (OER) electrocatalysts with earth-abundant elements is very important for sustainable H 2 generation via electrochemical water splitting. Here we design a crystalline-amorphous Ni–Fe–Al hybrid phosphides nanosheet arrays grown on NiFe foam for efficient OER application. Dynamic surface reorganization of phosphides at anodic/cathodic polarizations is probed by in situ Raman spectroscopy. The reconstructed amorphous Ni(Fe)OOH species are determined as the active phases that facilitate the OER process. This unique electrode shows highly catalytic activity toward water oxidation, achieving the current densities of 10 and 100 mA cm−2 at 181 and 214 mV in 1 M KOH, respectively. Meanwhile, it also exhibits excellent stability at a large current density of 100 mA cm−2 for over 60 h. This work reveals the dynamic structural transformation of pre-catalyst in realistic conditions and highlights the important role of oxyhydroxides as real reactive species in OER process with high activity. [Display omitted] • Ni–Fe–Al hybrid phosphides nanosheet arrays were synthesized for OER. • Dynamic self-reconstruction was revealed by in situ Raman spectroscopy. • Amorphous Ni(Fe)OOH species act as the real active phases. • Regenerated pre-catalyst shows excellent OER activity. [ABSTRACT FROM AUTHOR]

Metal foams with high surface/volume ratio and excellent electrical conductivity are widely used in water splitting. Herein, we report a redox process sculpturing commercial NiFe foams with dual-scale porosities as high efficient catalysts for water oxidation reactions. Through the oxidation-reduction process, many pores of few micrometres in size were formed on a porous NiFe backbone with a pore size of 50–300 μm. The pore morphology can be reasonably controlled by varying the oxidation temperature. Electrochemical measurement demonstrates that redox-NiFe foam exhibits greatly enhanced activity towards oxygen evolution reaction. Specifically, the redox-NiFe foam oxidized at 900 °C yields the best catalytic activity with an overpotential of 294 ± 3 mV to achieve the current density of 100 mA cm−2 in 1 M KOH, which is much lower than 402 ± 2 mV of initial NiFe foam. This work highlights the formation of highly porous microstructure in the original skeleton of NiFe foam. Furthermore, the redox sculptured NiFe foams can also function as effective skeletons for the loading of active catalysts, which thus can find wide applications in electrocatalysis and energy storage. • NiFe foams with dual-scale porosities were fabricated by a redox process. • Micropore structure can be engineered by controlling oxidation temperature. • Redox-NiFe foams exhibited greatly enhanced water oxidation activity. • Redox NiFe foam showed excellent durability. [ABSTRACT FROM AUTHOR]

Low thermal conductivity of most phase change materials (PCMs) limits the practical application of latent thermal energy storage. This study aims to investigate the role of the partial and gradient filling strategies of copper foam on the heat transfer characteristic of latent thermal energy storage. A visual test rig was built to capture the evolution of the melting front over time. An infrared camera and T-type thermocouples measured the temperature fields and temperature profiles at specific points, respectively. The melting rate, temperature distribution and storage efficiency were investigated and analyzed in detail. The melting rate of PCM first increases and then decreases with the increase of filling ratio, and reaches the maximum value when the filling ratio is 5/6. The application of partial filling strategy reduces the maximum temperature difference of PCM and enhances the stability of the system. In the application of gradient filling strategy, copper foam with larger porosity should be arranged close to the heating wall or above the cavity. Partial and gradient strategy can increase the melting rate of PCM by reducing or maintaining the filling quantity of metal foam, which is of great significance for the practical application of metal foam in latent energy storage. [Display omitted] • Visual test rig is built to study the effect of partial and gradient strategy of copper foam. • Partial and gradient copper foam with different structural parameters are designed. • Melting performance of partial and gradient strategy is higher than that of uniform strategy. • The evolution of melting interface is affected by different filling strategies. [ABSTRACT FROM AUTHOR]

Developing efficient and nonprecious electrocatalysts for oxygen evolution reaction (OER) is crucial for the hydrogen generation via water splitting. Here we report the direct growth of heterostructural Ni 2 P–Fe 2 P hybrid electrocatalysts on NiFe foams. The redox engineered NiFe foam (rNF) significantly enhances the OER performance. Among prepared catalysts, Ni 2 P–Fe 2 P/rNF performs the highest OER activity, driving the current densities of 10 and 100 mA cm−2 at low overpotentials of 218 and 270 mV in 1 M KOH, respectively. Meanwhile, it can maintain 100 mA cm−2 for 24 h without obvious degradation. The morphology and composition of NFP/rNF after OER test were carefully studied. This work suggests that self-supported bimetal phosphides of NFP/rNF is an efficient and durable electrode material for water oxidation. Heterostructural Ni2P-Fe2P hybrid electrocatalysts were direct grown on NiFe foams, which show excellent oxygen evolution activity and stability. Image 1 • The formation of micro-sized pores on the skeleton of NiFe foam (NF) substrate can enlarge surface area. • The heterogeneous Ni2P-Fe2P structure provides plentiful active sites for OER. • The Ni2P-Fe2P/ rNF foam exhibits an extraordinary electro catalytic performance. [ABSTRACT FROM AUTHOR]