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FeOOH nanowires were prepared and characterized with X-ray diffraction spectroscopy and scanning electron microscopy. A composite electrode consisting of FeOOH and Ni foam (FeOOH/Ni-foam) was fabricated, and its catalytic performance for oxygen evolution reaction (OER) was evaluated and compared with nanowire NiCoO/Ni-foam electrode. The mass current density of OER on FeOOH/Ni-foam is around three times of that on NiCoO/Ni-foam. Ni foam played a key role for the high activity of the FeOOH/Ni-foam. A synergistic mechanism of FeOOH and Ni was proposed to account for the superior catalytic performance of the FeOOH/Ni-foam electrode. Considering the low cost, abundant resource and environment-benign property of FeOOH, the FeOOH/Ni-foam electrode would be a promising anode for OER. [ABSTRACT FROM AUTHOR]

[Display omitted] • The carbonized recycled melamine sponge obtained excellent low-cost porous matrix. • FeNi@NCS shows lower reaction potential and higher electron transfer ability on UOR. • Successfully assembled the DBHPFC using urine as fuel. • DUHPFC presents excellent open circuit voltage. The direct urea fuel cell (DUFC) is a power generation equipment with urea-rich wastewater or urine as fuel source. It has the unique ability to purify sewage while simultaneously generating electricity, making it a highly efficient and environmentally friendly option. In this paper, pomegranate seed-like Ni nano-blocks and Fe nanosheets were synthesized by electrodeposition and chemical reduction and attached to the carbonized melamine sponge matrix. The N -doped carbon sponge (NCS) provided a large number of polyhedral holes, which allowed for efficient gas escape through channels. The combination of Fe reduces the initial urea oxidation potential, reaction activation energy and reaction resistance. The synthesized FeNi supported on N -doped carbon sponge composite (FeNi@NCS) has a catalytic current density of 625 mA cm−2 and a Tafel slope of 42.51 mV dec−1 for urea electrooxidation reaction (UOR). Assembling the direct urine-hydrogen peroxide fuel cell (DUrHPFC) resulted in the highest performance output. The open circuit voltage (OCV) was 0.98 V, and the peak power density reached 9.61 mW cm−2. The results show that the prepared catalyst provides an opportunity to solve the problems that hinder the development of urea green cycle at present. [ABSTRACT FROM AUTHOR]

The adoption of effective, minimal, and versatile electrocatalysts for water splitting to generate hydrogen fuels is of critical importance. The bulk of newly described materials have considerable onset potential, but their electrocatalytic activity is limited by weak electrical conductivity and a limited range of catalytic sites. The combination of a few precious metals added with transition metal-based compounds is a novel and captivating approach. Herein, cobalt ferrite oxide (Co 2 FeO 4) @ palladium oxide (PdO) nanostructures have been prepared through the combined use of hydrothermal and ultraviolet (UV) irradiation techniques. For hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics, the modified composition offers a high concentration of active sites, improved electrical conductivity, and stability. The Co, Fe, and Pd ions at the composite system's interface may affect the adsorption energy of reaction intermediates synergistically, enabling the process to continue with less potential. The electrocatalyst Co 2 FeO 4 @PdO demonstrates an excellent bifunctional approach to electrochemical water splitting (EWS) for HER and OER in alkaline medium. As-prepared electrocatalyst shows an overpotential value of 269 and 259 mV for HER and OER at 10 and 20 mA/cm2 current densities respectively. The low charge transfer resistance values such as 72.2 and 62.4 Ω and durability for 48 h has been observed toward HER and OER , support this material as an efficient and durable electrocatalyst for energy conversion systems. [Display omitted] • Effective Cobalt–Iron-Ferrite oxides and Palladium-oxide based bifunctional electrocatalyst. • Promising activity for HER and OER with lower Tafel slope values in the alkaline media. • Longer stability and durability for 20 h. [ABSTRACT FROM AUTHOR]

Development of efficient, low cost and multifunctional electrocatalysts for water splitting to harvest hydrogen fuels is a challenging task, but the combination of carbon materials with transition metal-based compounds is providing a unique and attractive strategy. Herein, composite systems based on cobalt ferrite oxide-reduced graphene oxide (Co 2 FeO 4) @(rGO) using simultaneous hydrothermal and chemical reduction methods have been prepared. The proposed study eliminates one step associated with the conversion of GO into rGO as it uses direct GO during the synthesis of cobalt ferrite oxide, consequently rGO based hybrid system is achieved in-situ significantly, the optimized Co 2 FeO 4 @rGO composite has revealed an outstanding multifunctional applications related to both oxygen evolution reaction (OER) and hydrogen counterpart (HER). Various metal oxidation states and oxygen vacancies at the surface of Co 2 FeO 4 @rGO composites guided the multifunctional surface properties. The optimized Co 2 FeO 4 @rGO composite presents excellent multifunctional properties with onset potential of 0.60 V for ORR, an overpotential of 240 mV at a 20 mAcm−2 for OER and 320 mV at a 10 mAcm−2 for HER respectively. Results revealed that these multifunctional properties of the optimized Co 2 FeO 4 @ rGO composite are associated with high electrical conductivity, high density of active sites, crystal defects, oxygen vacancies, and favorable electronic structure arisinng from the substitution of Fe for Co atoms in binary spinel oxide phase. These surface features synergistically uplifted the electrocatalytic properties of Co 2 FeO 4 @rGO composites. The multifunctional properties of the Co 2 FeO 4 @ rGO composite could be of high interest for its use in a wide range of applications in sustainable and renewable energy fields. Illustration of multifunctional surface properties of Co 2 FeO 4 @rGO composite. [Display omitted] • In situ rGO and cobalt ferrite oxide (Co 2 FeO 4 @rGO) composite is prepared. • The synthesized composite exhibited tri-functional water catalysis. • Composite shows an overpotential of 240 mV at a 20 mAcm−2 for OER. • A long term durability of 48 h was also demonstrated by composite material. [ABSTRACT FROM AUTHOR]

The rational design of efficient electrocatalysts for hydrogen peroxide electroreduction is essential to improve the performance of direct hydrogen peroxide fuel cells. In this study, we synthesized a Co 4 N/CoNC with a heterogeneous interface grown directly on nickel foam (NF) substrates as a highly active electrocatalyst for hydrogen peroxide (H 2 O 2) electroreduction (HPRR). Benefiting from the integrated three-dimensional structure with sufficient active sites, the high electrical conductivity, and the synergistic effect of the heterogeneous interfaces of Co 4 N and Co–N–C, the electrode provides superior H 2 O 2 electrocatalytic properties, with a current density up to 0.65 A cm−2 at −0.8 V vs. Ag/AgCl, Tafel slope at 34.86 mV dec−1 and low activation energy as 9.65 kJ mol−1 in alkaline medium. Our findings provide insights into the design of efficient H 2 O 2 electrocatalyst design. [Display omitted] • Co 4 N/CoNC heterointerface catalysts synthesized by simple hydrothermal and co-precipitation methods. • The unique structure of Co 4 N/CoNC provides a large exposure of the heterogeneous interface to the reaction environment. • Co 4 N/CoNC exhibit excellent catalytic activity and stability in the electroreduction of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

[Display omitted] • RuNi 1 Co 1 alloy nanoparticles embedded in the hollow carbon tubes with a mosaic structure was prepared. • The DFT calculations indicate that the addition of Ru could optimize the hydrogen adsorption free energy of Ni and Co sites. • RuNi 1 Co 1 @CMT exhibits considerable HER and OER activities, and a low cell voltage was required for the overall water splitting system. • RuNi 1 Co 1 @CMT || RuNi 1 Co 1 @CMT overall water splitting system can be driven by a solar panel, which realized green and sustainable hydrogen production. The development of efficient bifunctional catalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is essential for reducing the cost of hydrogen production by water splitting. Herein, hollow microtubes composed of RuNi 1 Co 1 alloy nanoparticles uniformly embedded in the carbon matrix (RuNi 1 Co 1 @CMT) are prepared through a simple impregnation followed by reduction. Benefiting from the unique mosaic structure and the synergistic effect between Ru and NiCo, RuNi 1 Co 1 @CMT achieves more exposed active sites and improved reaction kinetics. As a consequence, RuNi 1 Co 1 @CMT exhibits considerable catalytic activities with the overpotentials of 78 mV for HER and 299 mV for OER at 10 mA cm−2 in 1 M KOH. In addition, RuNi 1 Co 1 @CMT exhibits excellent stability for up to 30 h in both HER and OER processes at 20 mA cm−2, which is attributed to the protection of the RuNi 1 Co 1 alloy particles by the carbon layer. Furthermore, the assembled RuNi 1 Co 1 @CMT || RuNi 1 Co 1 @CMT overall water splitting system shows a cell voltage of 1.58 V at 10 mA cm−2. The density functional theory (DFT) calculations indicate that the addition of Ru can optimize the hydrogen adsorption free energy of Ni and Co sites. Finally, a solar panel-driven water splitting device is built, which can realize green and sustainable hydrogen production. The fabrication of RuNi 1 Co 1 @CMT provides a new way for the preparation of effective alloy nanomaterials for energy storage and conversion. [ABSTRACT FROM AUTHOR]

[Display omitted] Electrocatalytic water splitting used for generating clean and sustainable hydrogen (H 2) can be very promising to address current energy shortage and associated environmental issues. However, this methodology is severely impeded by the tardy oxygen evolution reaction (OER). Hence, designing a preferable kinetics and thermodynamics oxidation reaction that supersede OER is very significant for the energy-saving production of H 2. Herein, hollow needle-like copper cobalt sulfide was constructed on carbon cloth (CuCo 2 S 4 /CC) as a bifunctional electrocatalyst to accelerate H 2 generation and simultaneously convert ethanol into value-added acetic acid. Thanks to the synergistic effect and unique structure of Cu and Co, CuCo 2 S 4 /CC displays superior catalytic activity and durability in ethanol oxidation reaction (EOR) with a low potential of 1.38 V vs. RHE (@10 mA cm−2). Meanwhile, it exhibits excellent hydrogen evolution reaction (HER) performance. The homemade CuCo 2 S 4 /CC//CuCo 2 S 4 /CC ethanol–water electrolyser only demands a voltage of 1.59 V to deliver 10 mA cm−2, 150 mV less than that used for ordinary water splitting. This shows that the ethanol–water electrolyser elaborated here holds encouraging potential in the energy-saving production of H 2 and oxidation of ethanol into value-added acetic acid. This present work may open the way for the rational design of other electrocatalysts for efficient biomass oxidation reaction and relevant H 2 production applications. [ABSTRACT FROM AUTHOR]

• The CeS 2 incorporation modulates the internal electronic state. • Ce species stabilizes some of the surface sulphide against self-oxidation during OER process. • The strategy of iron dopant is conducive to induce plentiful S-defects. • The nanoparticles-rich structure affords ample holes and irregular flow channels. • Polyvalent Ce species provides great redox property, enhancing the electrocatalytic activity. Design and fabrication of high-efficiency nickel-rich electrocatalytic materials for sluggish oxygen evolution reaction (OER) remains a tremendous challenge. Modulating internal electronic state and accelerating charge transfer are two of vital means to optimizing electrocatalysts. In this work, nanoparticles-rich Fe-(CeS 2 /Ni 3 S 2) hybrid material with abundant heterointerfaces and sulfur-defects are facilely synthesized. The strategy of iron dopant is conducive to induce more sulfur defects. The cerium species can modulate the internal electronic state and stabilize some of the surface sulphide against self-oxidation during OER process. This self-supported heterogeneous material requires overpotentials of 254 and 372 mV to reach the current densities of 100 and 500 mA cm−2 in alkaline condition. The addition of urea or ethanol to the bath solution has been demonstrated as an efficient strategy for reducing the onset potential and decreasing energy consumption, thereby confirming the feasibility of applying this approach to energy-saving hydrogen production through electrolysis wastewater splitting. [ABSTRACT FROM AUTHOR]

Herein, the vertical thin nickel–iron layered double hydroxide nanosheets grown on the hills-like nickel framework (NiFe LDH/Ni@NF) are employed for the oxygen evolution reaction (OER), securing at the low overpotentials of 197 and 270 mV to obtain the current densities of 20 and 100 mA cm−2, respectively, with a Tafel slope of 73.34 mV dec−1. The electrodeposited nickel film induces the NiFe LDH nanosheets grow vertically and thinly. As well, the nickel abundant interfaces and inner space makes this catalyst effective for OER. It was further served as the OER electrode in a water splitting system coupled the Pt/C cathode, and a cell voltage was at 1.52 and 1.67 V to achieve the current density of 10 mA cm−2 and 50 mA cm−2. In addition, the water electrolyzer can suffer a long time of 24 h at 50 mA cm−2, showing the feasibility in a practical unbiased alkaline water splitting system. • The vertical thin Ni 4 Fe 1 LDH-16h was prepared on the hills-like nickel framework. • The crosslinked nanosheets can offer amounts of active sites for OER. • It achieves a low overpotential of 197 mV to drive 20 mA cm−2 for OER. • The assembled electrolyzer exhibits enhanced performance. [ABSTRACT FROM AUTHOR]

In this paper, we report the three-dimensional self-supported CoMoO 4 nanosheet clusters on the nickel foam (denoted as CoMoO 4 /NF) by a facile hydrothermal-calcination method for efficient hydrogen generation. As a result, the freestanding CoMoO 4 electrode exhibits an efficient electrochemical activity towards hydrogen evolution reaction, showing overpotentials as low as 68 and 178 mV at current densities of 10 and 100 mA cm−2 in the alkaline condition (1 M KOH), respectively, a Tafel slope value of 82 mV per decade. Moreover, the electrode exhibits remarkable electrochemical durability for 1000 cycles. Significantly, the water splitting electrolyzer assembled with CoMoO 4 /NF || NiFe LDH/NF (the nickel iron layered double hydroxide supported on the nickel foam) system achieved 20 mA cm−2 at 1.63 V, showing the CoMoO 4 /NF is promising for practical water splitting applications. • The low-cost and effective transition metal oxide of CoMoO 4 was adopted for hydrogen generation. • The open nanostructure can facilitate permeating electrolyte as well as releasing hydrogen molecules. • The crosslinked nanosheet clusters can offer amounts of active sites for hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

The exploitation of efficient and low-cost electrocatalysts for the oxygen evolution reaction (OER) is the key to the industrialization of the hydrogen production technology from water splitting. Herein, Ni 1 Fe 2 @Fe 2 O 3 composites with core-shell structure embedded in Metaplexis japonica fluff-derived carbon microtube matrix (Ni 1 Fe 2 @Fe 2 O 3 @C) are prepared by nitrate soaking and subsequent high-temperature calcination, which are used to catalyze the OER. The existence of carbon matrix greatly prevents the agglomeration of metal particles and creates an efficient electron transfer path for OER. The synergy among the carbon matrix, Ni 1 Fe 2 core and Fe 2 O 3 shell together enhances the OER performance, thus endowing Ni 1 Fe 2 @Fe 2 O 3 @C with the considerable catalytic activity with the overpotential of 271 mV at 10 mA cm−2 and a Tafel slope of 78 mV dec−1. Ni 1 Fe 2 @Fe 2 O 3 @C also shows good stability due to the double protection of metal particles by biomass carbon matrix and ultrathin Fe 2 O 3 shell. The water splitting device composed of Pt/C as the cathode and Ni 1 Fe 2 @Fe 2 O 3 @C as the anode exhibits water splitting activity close to that of Pt/C || RuO 2 system in alkaline medium, and the stability retention rate of the system reaches to 93 % after 30 h electrolysis. [Display omitted] • Ni 1 Fe 2 @Fe 2 O 3 composites with core-shell structure embedded in Metaplexis japonica fluff-derived carbon microtube matrix were prepared. • The existence of carbon matrix greatly prevents the agglomeration of metal particles and creates an efficient electron transfer path for OER. • Ni 1 Fe 2 @Fe 2 O 3 @C exhibits considerable catalytic activity with the low overpotential for OER. [ABSTRACT FROM AUTHOR]

The design of inexpensive bifunctional electrocatalysts with excellent catalytic activity is crucial for the cost reduction from water splitting. As a kind of biomass with hollow tubular structure, Metaplexis japonica fluff is expected to be a natural substrate for the growth of nanostructured electrocatalysts. Herein, nanowire-like NiCo precursors are grown on Metaplexis japonica fluff biomass substrates by hydrothermal method, which are then converted into carbon microtube supported NiCoP-NiS 2 composites (NiCoP-NiS 2 /CMT) by low-temperature phosphorization and sulfidation treatment. As expected, the biomass substrate provides a guiding role for the growth of NiCoP-NiS 2 nanowires, which is conducive to expose more active areas and promote charge transfer during the reaction. As a result, the obtained NiCoP-NiS 2 /CMT exhibits good electrocatalytic performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in 1 M KOH, which only requires overpotentials of 134 and 308 mV at 10 mA cm−2, respectively. In addition, the constructed symmetric water splitting device exhibits a cell voltage of 1.62 V at 10 mA cm−2, and it also displays good stability during the 24 h test. [Display omitted] [ABSTRACT FROM AUTHOR]

Exploring high-efficiency and low-cost electrocatalysts with outstanding durableness for oxygen evolution reaction (OER) is the key to practical production of eco-friendly hydrogen energy by water electrolysis technology, which remains challenging. In this paper, the tremella-like MnO 2 /(Fe,Ni) 3 S 4 hybrid nanostructures are supported on nickel foam matrix by a facile and governable method, with predominant OER properties in 1.0 M KOH solution. Profiting from the synergistic effect between MnO 2 and (Fe,Ni) 3 S 4 , this optimal MnO 2 /(Fe,Ni) 3 S 4 catalyst only requires 220 and 325 mV to fulfill current densities of 10 and 500 mA cm−2, respectively. Through the inheritance and optimization of MnO 2 and (Fe,Ni) 3 S 4 nanostructures, this hybrid catalyst possesses a large specific surface area, appropriate exposure active site and favorable electrical conductivity. Besides, the self-supported MnO 2 /(Fe,Ni) 3 S 4 electrode exhibits eminent stability at 10 and 100 mA cm−2 during the 20 h OER process. • 1.The tremella-like nanostructure provides plentiful active sites. • 2.Vast openings are beneficial to the conversion of water molecules. • 3.MnO 2 and (Fe,Ni) 3 S 4 form hybrid nanostructures. • 4.This unique hybrid material has a good synergistic effect. • 5.This electrocatalyst exhibits excellent OER activity and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • The hierarchical Ni-Fe phosphide nanosheets with numerous nanopores were constructed. • The Ni-Fe-P/NF shows superior catalytic activity and durability for both EOR and HER. • Hybrid-water cell exhibits lower energy consumption compared with water electrolysis. • The hybrid water electrolysis product is more valuable than the raw ethanol or O 2. Hydrogen (H 2) generated via water electrolysis exhibits great potential in addressing the urgent environmental and energy issues. Nevertheless, this approach is immensely handicapped by the tardy oxygen evolution reaction (OER). The ethanol oxidation reaction (EOR) can feasibly substitute the OER for hydrogen generation with less power expending on account of the more beneficial thermodynamics and kinetics. Herein, the hierarchical nickel–iron phosphide (Ni-Fe-P) nanosheet directly grown on Ni foam (NF) is proposed as a high-efficiency self-supported bifunctional electrocatalyst. Integrating the advantages of the unique architecture and the composition, the Ni-Fe-P/NF electrode displays highly alluring electrocatalytic activity and stability toward EOR as well as hydrogen evolution reaction (HER). The as-assembled Ni-Fe-P/NF//Ni-Fe-P/NF hybrid ethanol–water electrolyser only requires 1.53 V to supply 10 mA cm−2, outperforming the sole water splitting (1.66 V). Noteworthily, the liquid product of electrolysis is more meritorious than the raw material, highlighting that the hybrid ethanol–water electrolyser we elaborated possesses prodigious potentiality for application in energy-saving H 2 generation and the oxidation of ethanol into acetic acid. This work may provide an innovative strategy in designing and developing other high-efficiency organic molecule electrocatalysts and related energy-saving H 2 production applications in the future. [ABSTRACT FROM AUTHOR]

Strengthening electrical conductivity and multiple atomic interaction are benefit for improving activity of oxygen evolution reaction (OER). Herein, we synthesized Fe-Doped NiSe 2 nanospheres distribute on reduced graphene oxide sheets (Ni 0.7 Fe 0.3 Se 2 /rGO). The optimum ratio (30%) of rGO was ascertained by comparing the properties of catalysts with different rGO amounts. In alkaline electrolyte, the Ni 0.7 Fe 0.3 Se 2 /rGO-30% owns the better OER performance than those of Ni 0.7 Fe 0.3 Se 2 and NiSe 2 , ascribed to the unique architecture that Ni 0.7 Fe 0.3 Se 2 nanospheres decorate rGO. In the architecture, the rGO matrix increases conductivity, enlarges transfer rate of ions and electrons and promotes dispersion of Ni 0.7 Fe 0.3 Se 2. In addition, multiple atomic interaction of Ni/Fe atoms and the synergistic effect between the Ni 0.7 Fe 0.3 Se 2 and rGO enable the compound to be an efficient OER catalyst. Through the rational analysis, Ni 0.7 Fe 0.3 Se 2 /rGO-30% hybrid is promising as an effective non-noble metal catalyst for OER application. • The Ni 0.7 Fe 0.3 Se 2 nanospheres uniformly decorate the rGO. • Multiple atomic interaction contributes to better OER activities. • The rGO increases conductivity of composite and accelerates charge transfer rate. • The content of rGO in composites affects the OER performance. [ABSTRACT FROM AUTHOR]