The utilization of nanoporous copper (np-Cu) as a metallic actuator has gained attention in recent years due to its cost-effectiveness in comparison to other precious metals. Despite this, the enhancement of np-Cu’s actuation performance remains a challenge due to limitations in its strain amplitude and actuation rate. Additionally, np-Cu has been deemed as a promising material for solar absorption due to its localized surface plasmon resonance effect. However, practical applications such as solar steam generators (SSGs) utilizing np-Cu have yet to be documented. In this study, we present the development of hierarchically nanoporous copper (HNC) through the dealloying of a eutectic Al-Cu alloy. The hierarchical structure of the HNC features a combination of ordered flat channels and randomly distributed continuous nanopores, which work in synergy to improve actuation performance. The ordered flat channels, with a sub-micron scale, facilitate rapid mass transport of electrolyte ions, while the nano-sized continuous pores, due to their large specific surface area, enhance the induced strain. Our results indicate that the HNC exhibits improved actuation performance, with a two times increase in both strain amplitude and rate in comparison to other reported np-Cu. Additionally, the HNC, for the first time, showcases excellent solar steam generation capabilities, with an evaporation rate of 1.47 kg·m⁻²·h⁻¹ and a photothermal conversion efficiency of 92% under a light intensity of 1 kW·m⁻², which rivals that of nanoporous gold and silver film. The enhanced actuation performance and newly discovered solar steam generation properties of the HNC are attributed to its hierarchically porous structure.

With the rapid development of electronics, electric vehicles, and grid energy storage stations, higher requirements have been put forward for advanced secondary batteries. Liquid metal/alloy electrodes have been considered as a promising development direction to achieve excellent electrochemical performance in metal-ion batteries, due to their specific advantages including the excellent electrode kinetics and self-healing ability against microstructural electrode damage. For conventional liquid batteries, high temperatures are needed to keep electrode liquid and ensure the high conductivity of molten salt electrolytes, which also brings the corrosion and safety issues. Ga-based metal/alloys, which can be operated at or near room temperature, are potential candidates to circumvent the above problems. In this review, the properties and advantages of Ga-based metal/alloys are summarized. Then, Ga-based liquid metal/alloys as anodes in various metal-ion batteries are reviewed in terms of their self-healing ability, battery configurations, working mechanisms, and so on. Furthermore, some views on the future development of Ga-based electrodes in batteries are provided.

Given the challenges brought by the shortage of freshwater resources, solar water evaporation has been regarded as one of the most promising technologies for harnessing abundant sunlight to harvest clean water from the sea. Nanostructured metals have attracted extensive attention in solar water evaporation due to their localized surface plasmon resonance effect, but highly porous metallic films with high evaporation efficiency are challenging. Herein, a self-supporting black nanoporous silver (NP-Ag) film was fabricated by dealloying of an extremely dilute Al₉₉Ag₁ alloy. The choice of the dilute precursor guarantees the formation of the NP-Ag film with high porosity (96.5%) and low density (0.3703 g·cm^–3, even smaller than the lightest metal lithium). The three-dimensional ligament-channel network structure and the nanoscale (14.6 nm) of ligaments enable the NP-Ag film to exhibit good hydrophilicity and broadband absorption over 200‒2,500 nm. More importantly, the solar evaporator based on the NP-Ag film shows efficient solar steam generation, including the efficiency of 92.6%, the evaporation rate of 1.42 kg·m^–2·h^–1 and good cycling stability under one sun irradiation. Moreover, the NP-Ag film exhibits acceptable seawater desalination property with the ion rejection for Mg²⁺, Ca²⁺, K⁺ and Na⁺ more than 99.3%. Our findings could provide a new idea and inspiration for the design and fabrication of metal-based photothermal films in real solar evaporation applications.

Highly active and stable electrocatalysts to produce hydrogen through water splitting are crucial for clean energy systems but are still challenging. Herein, a novel self-templating strategy was proposed to synthesize one-dimensional nanoporous RhNi alloy nanowires through combining metallurgical eutectic solidification and microalloying with chemical dealloying. In-situ X-ray diffraction and ex-situ characterizations reveal that the Al matrix served as a template to guide the growth of the Al₃(Ni, Rh) nanowires during eutectic solidification of Al-Ni-Rh precursor and was completely removed in the dealloying process. Meanwhile, the nanowire morphology could be well retained and the dealloying of Al₃(Ni, Rh) led to the formation of nanoporous RhNi alloy nanowires. The length scale of the RhNi nanowires could be facilely regulated by changing the solidification conditions. More importantly, the RhNi catalysts show excellent electrocatalytic activity and stability towards hydrogen evolution reaction in both acidic and alkaline media, which has been rationalized by density functional theory calculations.

Combining multiple metal elements into one nanostructure merits untold application potential but is still a challenge for the traditional bottom-up synthesis method. Herein, we propose a eutectic-directed self-templating strategy to prepare two multi-component nanostructured alloys (PtPdRhIrNi (D-SN) and NiPtPdRhIrAl (D-SS)) through the combination of rapid solidification with dealloying. The PtPdRhIrNi nanoporous nanowires (NPNWs) represent a new family of high-entropy alloys (HEAs) containing delicate hierarchical nanostructure with ultrafine ligament sizes of ~ 2 nm in addition to one-dimensional (1D) morphology. Moreover, the PtPdRhIrNi NPNWs display excellent electrocatalytic activity and stability toward hydrogen evolution reaction, with the low overpotential of 22 and 55 mV to afford a current density of 10 mA·cm⁻² in 0.5 M H₂SO₄ and 1.0 M KOH electrolytes, respectively. The enhanced electrocatalytic performance can be attributed to the high-entropy effect favoring the surface electronic structure for the optimized activity, the promotion impact of Ni, 1D morphology facilitating the electron transport, and the nanoporous structure promoting the electrolyte diffusion.

Among various efficient electrocatalysts for water splitting, CoFe and NiFe-based oxides/hydroxides are typically promising candidates thanks to their extraordinary activities towards oxygen evolution reaction (OER). However, the endeavor to advance their performance towards overall water splitting has been largely impeded by the limited activities for hydrogen evolution reaction (HER). Herein, we present a CoFeNi ternary metal-based oxide (CoFeNi-O) with impressive hierarchical bimodal channel nanostructures, which was synthesized via a facile one-step dealloying strategy. The oxide shows superior catalytic activities towards both HER and OER in alkaline solution due to the alloying effect and the intrinsic hierarchical porous structure. CoFeNi-O loaded on glass carbon electrodes only requires the overpotentials as low as 230 and 278 mV to achieve the OER current densities of 10 and 100 mA·cm^-2, respectively. In particular, extremely low overpotentials of 200 and 57.9 mV are sufficient enough for Ni foam-supported CoFeNi-O to drive the current density of 10 mA·cm^-2 towards OER and HER respectively, which is comparable with or even better than the already-developed state-of-the-art non-noble metal oxide based catalysts. Benefiting from the bifunctionalities of CoFeNi-O, an alkaline electrolyzer constructed by the Ni foam-supported CoFeNi-O electrodes as both the anode and the cathode can deliver a current density of 10 mA·cm^-2 at a fairly low cell-voltage of 1.558 V. In view of its electrocatalytic merits together with the facile and cost-effective dealloying route, CoFeNi-O is envisioned as a promising catalyst for future production of sustainable energy resources.

Magnesium ion batteries are emerging as promising alternatives to lithium ion batteries because of their advantages including high energy density, dendrite-free features and low cost. Nevertheless, one of the major challenges for magnesium ion batteries is the kinetically sluggish magnesium insertion/extraction and diffusion in electrode materials. Aiming at this issue, biphase eutectic-like bismuth-tin film is designed herein to construct a self-supporting anode with interdigitated phase distribution and hierarchically porous structure, and further fabricated by a facile one-step magnetron cosputtering route. As benchmarked with single-phase bismuth or tin film, the biphase bismuth-tin film delivers high specific capacity (538 mAh/g at 50 mA/g), excellent rate performance (417 mAh/g at 1, 000 mA/g) and good cycling stability (233 mAh/g at the 200th cycle). The superior magnesium storage performance of the sputtered bismuth-tin film could be attributed to the synergetic effect of the interdigitated bismuth/tin phase distribution, hierarchically porous structure and biphase buffering matrices, which could increase ionic transport channels, shorten diffusion lengths and reduce total volume changes.

Transition-metal dichalcogenides (TMDs) exhibit immense potential as lithium/ sodium-ion electrode materials owing to their sandwich-like layered structures. To optimize their lithium/sodium-storage performance, two issues should be addressed: fundamentally understanding the chemical reaction occurring in TMD electrodes and developing novel TMDs. In this study, WSe₂ hexagonal nanoplates were synthesized as lithium/sodium-ion battery (LIB/SIB) electrode materials. For LIBs, the WSe₂-nanoplate electrodes achieved a stable reversible capacity and a high rate capability, as well as an ultralong cycle life of up to 1,500 cycles at 1,000 mA·g^–1. Most importantly, in situ Raman spectroscopy, ex situ X-ray diffraction (XRD), transmission electron microscopy, and electrochemical impedance spectroscopy measurements performed during the discharge–charge process clearly verified the reversible conversion mechanism, which can be summarized as follows: WSe₂ + 4Li⁺ + 4e^– ↔ W + 2Li₂Se. The WSe₂ nanoplates also exhibited excellent cycling performance and a high rate capability as SIB electrodes. Ex situ XRD and Raman spectroscopy results demonstrate that WSe₂ reacted with Na⁺ more easily and thoroughly than with Li⁺ and converted to Na₂Se and tungsten in the 1^st sodiated state. The subsequent charging reaction can be expressed as Na₂Se → Se + 2Na⁺ + 2e^–, which differs from the traditional conversion mechanism for LIBs. To our knowledge, this is the first systematic exploration of the lithium/sodium-storage performance of WSe₂ and the mechanism involved.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are crucial processes for energy conversion/storage systems, such as fuel cells, metal–air batteries, and water splitting. However, both reactions are severely restricted by their sluggish kinetics, thus requiring highly active, cost-effective, and durable electrocatalysts. Herein, we develop novel bifunctional nanocatalysts through surface nanoengineering of dealloying-driven nanoporous gold (NPG). Pd overlayers were precisely deposited onto the NPG ligament surface by epitaxial layer-by-layer growth. More importantly, the obtained NPG-Pd overlayer nanocatalysts exhibit remarkably enhanced electrocatalytic activities toward both the ORR and OER in alkaline media, benchmarked against a stateof- the-art Pt/C catalyst. The improved electrocatalytic performance is rationalized by the unique three-dimensional nanoarchitecture of NPG, enhanced Pd utilization efficiency from precise control of the Pd overlayers, and change in electronic structure, as revealed by density functional theory calculations.

Development of high-performance oxygen reduction reaction (ORR) catalysts is crucial to improve proton exchange membrane fuel cells. Herein, a multicomponent nanoporous PdCuTiAl (np-PdCuTiAl) electrocatalyst has been synthesized by a facile one-step dealloying strategy. The np-PdCuTiAl catalyst exhibits a three-dimensional bicontinuous interpenetrating ligament/channel structure with an ultrafine length scale of ~3.7 nm. The half-wave potential of np PdCuTiAl is 0.873 V vs. RHE, more positive than those of PdC (0.756 V vs. RHE) and PtC (0.864 V vs. RHE) catalysts. The np-PdCuTiAl alloy shows a 4-electron reaction pathway with similar Tafel slopes to PtC. Remarkably, the half-wave potential shows a negative shift of only 12 mV for np-PdCuTiAl in the presence of methanol, and this negative shift is much lower than those of the PdC (50 mV) and PtC (165 mV) catalysts. The enhanced ORR activity of np-PdCuTiAl has been further rationalized through density functional theory calculations.