Hydrogels are investigated broadly in flexible sensors which have been applied into wearable electronics. However, further application of hydrogels is restricted by the ambiguity of the sensing ...mechanisms, and the multi-functionalization of flexible sensing systems based on hydrogels in terms of cost, difficulty in integration, and device fabrication remains a challenge, obstructing the specific application scenarios. Herein, cost-effective, structure-specialized and scenario-applicable 3D printing of direct ink writing (DIW) technology fabricated two-dimensional (2D) transition metal carbides (MXenes) bonded hydrogel sensor with excellent strain and temperature sensing performance is developed. Gauge factor (GF) of 5.7 (0 - 191% strain) and high temperature sensitivity (-5.27% °C
) within wide working range (0 - 80 °C) can be achieved. In particular, the corresponding mechanisms are clarified based on finite element analysis and the first use of in situ temperature-dependent Raman technology for hydrogels, and the printed sensor can realize precise temperature indication of shape memory solar array hinge.
Splitting water into hydrogen by electrolysis using renewable electricity is one of the promising routes for green hydrogen production. The key dilemma for this electrochemical route is the extremely ...high overpotentials required for oxygen evolution reaction at the anode. Innovative strategies are desirable to fabricate inexpensive metal-based multifunctional catalysts with robust catalytic performance and large-current durability for electrochemical hydrogen production in freshwater or urea-containing water. Here we report the rational design and synthesis of hydrangea-like CoP/Ni
3
FeN heterostructure arrays as excellent multifunctional electrocatalysts for both alkaline water and urea electrolysis. This catalyst presents superb trifunctional catalytic activities and outstanding large-current durability in basic media, requiring ultralow potentials of −0.160, 1.538 and 1.419 V to facilitate hydrogen, oxygen evolution and urea oxidation reactions (HER, OER and UOR) at an extremely large current density of 1000 mA cm
−2
, respectively. Remarkably, the as-constructed two-electrode cells using this electrocatalyst as both the cathode and anode demand extremely low cell voltages of 1.577 and 1.668 V to deliver 500 mA cm
−2
stably for urea and water electrolysis, respectively, suggesting its superb activity and outstanding stability for trifunctional catalysis.
Operando
Raman spectroscopic studies in combination with density functional theory calculations validate that the CoP/Ni
3
FeN hybrid can greatly facilitate the formation of active metal (oxy)hydroxide species for both OER and UOR, and also reduce the adsorption energy barriers of *H
2
O and *H intermediates for HER. This work provides an effective pathway for developing multifunctional catalysts for electrochemical hydrogen production at low voltages whenever fresh or urea-containing water is available.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Designing highly active electrocatalysts for both the oxygen evolution and urea oxidation reactions (OER and UOR) with good durability at large current densities is very significant for greatly ...reducing the power consumption of water electrolysis and wastewater degradation. However, very few electrocatalysts simultaneously exhibit outstanding catalytic activities and large-current durability for both the oxygen evolution and urea oxidation reactions. Herein, we report a bifunctional nanoporous Fe-rich nitride hybrid electrocatalyst possessing extraordinary catalytic OER and UOR activities, as evidenced by extremely small potentials of 1.518 and 1.372 V with impressive long-term durability at a current density of 500 mA cm
−2
for both OER and UOR in base, respectively. Thus far, this is one of the best electrocatalysts embedding excellent OER and UOR properties in a single electrocatalyst. In particular, combined with an efficient NiMoO
4
-H
2
catalyst for the HER, we have actualized the commercially viable current density of 500 mA cm
−2
at 1.623 V and 1.472 V for overall water and urea electrolysis with outstanding long-term durability, respectively, outperforming most water or urea electrolysers reported hitherto. This work offers a novel approach to develop multifunctional electrocatalysts from earth-abundant elements for the energy-efficient hydrogen production and pollution treatment of urea-rich wastewater.
Iron is a good enhancer for boosting the sluggish water and urea oxidation reactions with low potentials of 1.518 and 1.372 V, respectively, which further actualize 500 mA cm
−2
at 1.623 and 1.472 V stably for water and urea electrolysis, respectively.
Seawater is the most abundant natural water resource in the world, which is an inexhaustible and low‐cost feedstock for hydrogen production by alkaline water electrolysis. It is appearling to develop ...robust and stable electrocatalysts for alkaline seawater electrolysis. However, the development of seawater electrolysis is seriously impeded by anodic chloride corrosion and chlorine evolution reaction, and few non‐noble electrocatalysts show prominent catalytic performance and excellent durability. Here, a heterogeneous electrocatalyst constructed by in situ growing highly dispersed iron‐rich bimetallic phosphide nanoparticles on metallic Ni3N (Fe2−2xCo2xP/Ni3N), which exhibits outstanding bifunctional catalytic activities for alkaline seawater splitting, is reported. The optimal (Fe0.74Co0.26)2P/Ni3N and Fe2P/Ni3N electrocatalysts demand only 113 and 212 mV to afford 100 mA cm−2 for hydrogen and oxygen evolution reactions (HER and OER) in 1 m KOH, respectively, thus substantially expediting overall water/seawater electrolysis at 100 mA cm−2 with 1.592/1.645 V. Particularly, Fe2P/Ni3N displays an unprecedented overpotential of 302 mV at 500 mA cm−2, which represents the best alkaline seawater oxygen evolution activity among the ever‐reported non‐noble electrocatalysts; and thus substantially expedites overall water/seawater splitting at 500 mA cm−2 with 1.701/1.768 V, surpassing most of the reported non‐noble lectrocatalysts. This work provides a new approach for developing high‐performance electrocatalysts for seawater splitting.
A most abundant and least expensive transition metal iron‐rich heterogeneous catalyst is in situ constructed on porous Ni3N support as high‐performance electrocatalyst for seawater splitting. The optimal catalyst displays low overpotentials of 225 and 302 mV to deliver 100 and 500 mA cm−2 for oxygen evolution in alkaline seawater, substantially expediting overall seawater electrolysis at 100 and 500 mA cm−2 with 1.645/1.768 V, respectively.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Earth‐abundant layered tungsten disulfide (WS2) is a well‐known electrocatalyst for acidic hydrogen evolution, but it becomes rather sluggish for alkaline hydrogen or oxygen evolution due to the ...low‐density edge sites, poor conductivity, and unfavorable water dissociation behavior. Here, an interfacial engineering strategy to construct an efficient bifunctional electrocatalyst by in situ growing N‐doped WS2 nanoparticles on highly conductive cobalt nitride (N‐WS2/Co3N) for concurrent hydrogen evolution reaction (HER) and urea oxidation reaction (UOR) is demonstrated. Benefiting from the good conductivity of Co3N, rich well‐oriented edge sites and water‐dissociation sites at the nanoscale interfaces between N‐WS2 and Co3N, the resultant N‐WS2/Co3N exhibits remarkable HER activity in 1 m potasium hydroxide (KOH) requiring a small overpotential of 67 mV at 10 mA cm−2 with outstanding long‐term durability at 500 mA cm−2, representing the best alkaline hydrogen‐evolving activity among reported WS2 catalysts. In particular, this hybrid catalyst also shows exceptional catalytic activities toward theurea oxidation reaction featured by very low potentials of 1.378 and 1.41 V to deliver 100 and 500 mA cm−2 along with superb large‐current stability in 1 m KOH + 0.5 m urea. Moreover, the assembled two‐electrode cell delivers the industrially practical current density of 500 mA cm−2 at a low cell voltage of 1.72 V with excellent durability in alkaline urea‐containing solutions, outperforming most MoS2‐like bifunctional electrocatalysts for overall water splitting reported hitherto. This work provides a promising avenue for the development of high‐performance WS2‐based electrocatalysts for alkaline water splitting.
An in situ interfacial engineering strategy is introduced to construct a highly efficient and stable hybrid catalyst consisting of N‐doped WS2 particles on Co3N, which presents interesting bifunctional catalytic properties for the hydrogen evolution reaction and nitrogenous nucleophile electrooxidation, demanding only 1.72 V to stably deliver 500 mA cm−2 for electrochemical hydrogen production.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The key dilemma for green hydrogen production via electrocatalytic water splitting is the high overpotential required for anodic oxygen evolution reaction (OER). Co/Fe‐based materials show superior ...catalytic OER activity to noble metal‐based catalysts, but still lag far behind the state‐of‐the‐art Ni/Fe‐based catalysts probably due to undesirable side segregation of FeOOH with poor conductivity and unsatisfied structural durability under large current density. Here, a robust and durable OER catalyst affording current densities of 500 and 1000 mA cm−2 at extremely low overpotentials of 290 and 304 mV in base is reported. This catalyst evolves from amorphous bimetallic FeOOH/Co(OH)2 heterostructure microsheet arrays fabricated by a facile mechanical stirring strategy. Especially, in situ X‐ray photoelectron spectroscopy (XPS) and Raman analysis decipher the rapid reconstruction of FeOOH/Co(OH)2 into dynamically stable Co1‐xFexOOH active phase through in situ iron incorporation into CoOOH, which perform as the real active sites accelerating the rate‐determining step supported by density functional theory calculations. By coupling with MoNi4/MoO2 cathode, the self‐assembled alkaline electrolyzer can deliver 500 mA cm−2 at a low cell voltage of 1.613 V, better than commercial IrO2(+)||Pt/C(‐) and most of reported transition metal‐based electrolyzers. This work provides a feasible strategy for the exploration and design of industrial water‐splitting catalysts for large‐scale green hydrogen production.
An exceptional and stable oxygen‐evolving electrocatalyst is developed from self‐reconstruction of amorphous bimetallic FeOOH/Co(OH)2 microsheet arrays through a mechanical stirring strategy, yielding a current densities of 500 and 1000 mA cm−2 at low overpotentials of 290 and 304 mV. This catalyst rapidly reconstructs into Co1‐xFexOOH species through in situ iron incorporation into CoOOH as confirmed by in situ X‐ray photoelectron, Raman spectroscopic studies, and theoretical calculations.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Electrocatalytic water splitting for generating green hydrogen is regarded as one of the most promising pathways to change the global energy structure and achieve the global mission of carbon ...neutrality. Despite ever-increasing research progress at low current densities (<100 mA cm−2) in laboratory, the water electrolysis still faces several challenges under industrially-relevant current densities (≥200 mA cm−2), such as corrosion, catalyst activity and stability issues. Thus, pursuing and designing cost-effective electrocatalysts with superior activity and stability under large current density is crucial for large-scale water splitting. This review first summarizes the fundamentals of water electrolysis both in alkaline freshwater and seawater and approaches for evaluating catalytic activity. Then, it concentrates on the innovative strategies for rational design of non-noble electrocatalysts toward alkaline water splitting and direct seawater splitting. Finally, the challenges and opportunities are highlighted for the development of catalysts toward large-current-density alkaline freshwater/seawater electrolysis.
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•This review summarizes the fundamentals of water electrolysis both in alkaline water and seawater and approaches for evaluating catalytic performance.•This review concentrates on the innovative strategies for design of electrocatalysts toward alkaline water splitting and direct seawater splitting at large current density.•The challenges and opportunities are highlighted for the development of catalysts toward large-current-density alkaline water/seawater electrolysis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Alkaline water electrolysis is a commercially viable technology for green H2 production using renewable electricity from intermittent solar or wind energy, but very few non‐noble bifunctional ...catalysts simultaneously exhibit superb catalytic efficiency and stability at large current densities for hydrogen and oxygen evolution reactions (HER and OER, respectively), especially for iron‐based catalysts. Given that iron is the most abundant and least expensive transition metal, iron‐based compounds are very attractive low‐cost targets as active electrocatalysts for bifunctional water splitting with large‐current durability. Herein, the in situ construction of a self‐supported Fe2P/Co2N porous heterostructure arrays possessing superb bifunctional catalytic activity in base is reported, featured by low overpotentials of 131 and 283 mV to attain a current density of 500 mA cm−2 for HER and OER, respectively, outperforming most of non‐noble bifunctional electrocatalysts reported hitherto. Particularly, this hybrid catalyst also displays an excellent overall water splitting activity, requiring low voltages of 1.561 and 1.663 V to attain 100 and 500 mA cm−2 with excellent durability in 1 m KOH, respectively. Most importantly, the catalyst is stable for >120 h, even when the current density is 500 mA cm−2, which is prominently superior to IrO2(+)//Pt(−) coupled noble electrodes, and is among the very best bifunctional catalysts reported thus far. Detailed theoretical calculations reveal that the interfacial interaction between Fe2P and Co2N can further improve the H* binding energy at the iron sites.
Self‐supported Fe2P/Co2N porous heterostructure arrays are in situ constructed with abundant iron sites exposing at the surface, which presents superb bifunctional catalytic activity for hydrogen and oxygen evolution reactions in base, substantially expediting the overall water splitting at 500 mA cm−2 with only 1.663 V, prominently superior to IrO2(+)//Pt(−) coupled electrodes and most of non‐noble bifunctional electrocatalysts.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Developing efficient non‐noble and earth‐abundant hydrogen‐evolving electrocatalysts is highly desirable for improving the energy efficiency of water splitting in base. Molybdenum disulfide (MoS2) is ...a promising candidate, but its catalytic activity is kinetically retarded in alkaline media due to the unfavorable water adsorption and dissociation feature. A heterogeneous electrocatalyst is reported that is constructed by selenium‐doped MoS2 (Se‐MoS2) particles on 3D interwoven cobalt diselenide (CoSe2) nanowire arrays that drives the hydrogen evolution reaction (HER) with fast reaction kinetics in base. The resultant Se‐MoS2/CoSe2 hybrid exhibits an outstanding catalytic HER performance with extremely low overpotentials of 30 and 93 mV at 10 and 100 mA cm–2 in base, respectively, which outperforms most of the inexpensive alkaline HER catalysts, and is among the best alkaline catalytic activity reported so far. Moreover, this hybrid catalyst shows exceptional catalytic performance with very low overpotentials of 84 and 95 mV at 10 mA cm–2 in acidic and neutral electrolytes, respectively, implying robust pH universality of this hybrid catalyst. This work may provide new inspirations for the development of high‐performance MoS2‐based HER electrocatalysts in unfavorable basic media for promising catalytic applications.
A heterogeneous catalyst constructed by selenium‐doped molybdenum disulfide particles supporting on interwoven cobalt diselenide nanowire arrays is developed to exhibit promising pH‐universal hydrogen evolution with extremely low overpotentials of 30 and 93 mV at 10 and 100 mA cm–2 in base solution, and also very low overpotentials of 84 and 95 mV at 10 mA cm–2 in acidic and neutral electrolytes, respectively.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Alkaline water electrolysis is an advanced technology for scalable H2 production using surplus electricity from intermittent energy sources, but it remains challenging for non‐noble electrocatalysts ...to split water into hydrogen and oxygen efficiently, especially for tungsten disulfide (WS2)‐based catalysts. Density functional theory calculations in combination with experimental study are used to establish a multi‐site engineering strategy for developing robust WS2‐based hybrid electrocatalyst on mesoporous bimetallic nitride (Ni3FeN) nanoarrays for bifunctional water splitting. This ingenious design endows the catalyst with numerous edge sites chemically bonded with the conductive scaffold, which are favorable for water dissociation and hydrogen adsorption. Benefiting from the synergistic advantages, the N‐WS2/Ni3FeN hybrid exhibits exceptional bifunctional properties for hydrogen and oxygen evolution reactions (HER and OER) in base with excellent large‐current durability, requiring 84 mV to afford 10 mA cm−2 for HER, and 240 mV at 100 mA cm−2 for OER, respectively. Assembling the catalytic materials as both the anode and cathode to construct an electrolyzer, it is actualized very good activities for overall water splitting with only 1.5 V to deliver 10 mA cm−2, outperforming the IrO2(+)//Pt(−) coupled electrodes and many non‐noble bifunctional electrocatalysts thus far. This work provides a promising avenue for designing WS2‐based heterogeneous electrocatalysts for water electrolysis.
Density functional theory calculations in combination with experimental study are used to establish a multi‐site engineering strategy for developing robust WS2‐based hybrid electrocatalyst on mesoporous bimetallic nitride nanoarrays for bifunctional water splitting in base, requiring 84 mV to afford 10 mA cm−2 for hydrogen evolution reaction, and 240 mV at 100 mA cm−2 for oxygen evolution reaction with excellent large‐current durability.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
