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The development and utilization of electrochemical energy conversion and storage devices can maximize intermittent renewable energy and balance environmental issues. Aqueous metal‐redox bicatalyst batteries, incorporating value‐added electro‐reduction reactions during discharge process at the cathode, are considered a particularly attractive alternative for simultaneous electricity generation and valuable chemical production. In this review, for the first time, a holistic and subtle description of value‐added metal‐redox bicatalyst batteries is made, focusing on recent efforts to optimize the energy conversion/chemical production‐involved cathodic discharging reactions, including CO2 reduction reaction (CO2RR), nitrogen reduction reaction (NRR), nitric oxide reduction reaction (NORR), nitrate reduction reaction (NO3−RR), nitrite reduction reaction (NO2−RR), hydrogen evolution reaction (HER), and acetylene reduction reaction (ARR). A macroscopic understanding of design principles in terms of anodes, cathodes, and reaction parameters is provided. Some mechanism explorations, feasibility analyses, technoeconomic assessments, device combinations, and associated comparisons are involved to deepen the understanding of different systems and evaluate their application prospects. Perspectives on and opportunities for future research directions are also outlined. [ABSTRACT FROM AUTHOR]

Highlights: Ultrathin P and Fe co-doped NiSe2 nanosheets supported on modified Ni foam are synthesized, which shows desirable bifunctional electrocatalytic hydrogen evolution reaction (HER)/hydrazine oxidation reaction (HzOR) performance in hydrazine-assisted water electrolysis and Zn-Hz battery. The coexistence of P and Fe heteroatoms induces an accelerated "2 + 2" reaction mechanism with a two-step HER process and a two-step HzOR step. Hydrazine-assisted water electrolysis is a promising energy conversion technology for highly efficient hydrogen production. Rational design of bifunctional electrocatalysts, which can simultaneously accelerate hydrogen evolution reaction (HER)/hydrazine oxidation reaction (HzOR) kinetics, is the key step. Herein, we demonstrate the development of ultrathin P/Fe co-doped NiSe2 nanosheets supported on modified Ni foam (P/Fe-NiSe2) synthesized through a facile electrodeposition process and subsequent heat treatment. Based on electrochemical measurements, characterizations, and density functional theory calculations, a favorable "2 + 2" reaction mechanism with a two-step HER process and a two-step HzOR step was fully proved and the specific effect of P doping on HzOR kinetics was investigated. P/Fe-NiSe2 thus yields an impressive electrocatalytic performance, delivering a high current density of 100 mA cm−2 with potentials of − 168 and 200 mV for HER and HzOR, respectively. Additionally, P/Fe-NiSe2 can work efficiently for hydrazine-assisted water electrolysis and Zn-Hydrazine (Zn-Hz) battery, making it promising for practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • Detailed ATR-SEIRAS study of the cation effects on CO 2 RR on practical Pd/C catalysts. • Spectral evidence of increased interfacial CO 2 concentration and electric field by larger cations. • Mechanistic understanding of cation effects on potential dependent CO 2 RR pathways. Electrochemical carbon dioxide (CO 2) reduction reaction (CO 2 RR) has long been known to be affected by the electrolyte cations, yet the interpretations of these effects remain controversial. In this work, taking advantage of the unique catalytic characteristics of Pd, we investigated the cation effects on the CO 2 RR. It was found that the productions of formate and carbon monoxide (CO) are accelerated, and the competitive hydrogen evolution reaction (HER) is suppressed on Pd surfaces by larger cations. Detailed ATR-SEIRAS measurements revealed the promotion of CO 2 RR comes from two aspects. First, the CO 2 molecules can be concentrated at the electrode–electrolyte interface by larger cations through electrostatic interaction. Second, a stronger interfacial electric field brought by the larger cations can accelerate the CO 2 RR and stabilize the negatively charged intermediates. The potential-dependent spectral transitions of adsorbed CO and interfacial water shed new light on the cation-dependent electric double layer structures. In light of these findings, the cation effects on the formate and CO pathways at different overpotentials were further revealed. [ABSTRACT FROM AUTHOR]

The chemistry of the diiron dithiolato hexacarbonyl complex Fe2(μ‐edt)(CO)6 (edt, 1,2‐ethanedithiolate) has received special attention, largely because that its structure is similar with the active site of [FeFe]‐hydrogenase. In order to enrich the chemistry of complex Fe2(μ‐edt)(CO)6 and synthesize new hydrogen evolution catalysts, a new route to the diiron dithiolato hexacarbonyl complex Fe2(μ‐edt)(CO)6 was described. Reaction of Fe3(CO)12 and Me3SiSCH2CH2SSiMe3 in the presence of Et3N at 80 °C afforded Fe2(μ‐edt)(CO)6 in 90 % yield. Furthermore, reaction of Fe2(μ‐edt)(CO)6 and aminodiphosphine ligands (Ph2P)2NC6H4R (R=−3‐CCH, 4‐CCH) produced the new PNP‐chelated diiron dithiolato complexes Fe2(μ‐edt)(CO)4{κ2‐(Ph2P)2NC6H4R} (1 and 2). All the complexes were characterized by elemental analysis, IR, NMR spectroscopy, and particularly for 1 and 2 by X‐ray single diffraction analysis. In addition, the electrochemical results indicated that 1 and 2 could be considered as electrocatalysts for hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]

A rational structural design of electrodes with high electron conductivity, sufficient material interfaces/defects and a regulated charge transfer pathway can be applied in broad practical electrochemical application fields. A triple-layered PPy@NiCo LDH/FeCo2O4 hybrid with a tri-metal hybrid nanowire and conductive PPy coating layer is fabricated via a one-step hydrothermal reaction and in situ polymerization. NiCo LDH/FeCo2O4 nanowire arrays with a layered crystalline structure are synthesized via an in situ dissolution-growth method, where the partially etched nickel foam substrate subsequently acts as the Ni source. The NiCo LDH/FeCo2O4 nanowire arrays together with the ultrathin PPy coating layer can form bi-continuous conductive networks, numerous crystalline edges and structural interfaces to increase the electron transfer rate and the active/adsorption sites, which can further promote the energy storage and electrocatalytic activity. The bi-functional PPy@NiFeCo/NF-4 electrode exhibits a high areal capacitance (9.24 F cm−2 at 5 mA cm−2) and excellent rate capability (90.5% retention from 5 to 30 mA cm−2) as a supercapacitor and achieves a small overpotential (244 mV at 50 mA cm−2) and Tafel slope (64.39 mV dec−1) as an electrocatalytic OER electrode. [ABSTRACT FROM AUTHOR]

Lithium metal is one of the most promising anode materials for high-energy-density Li batteries. However, low stability caused by dendrite growth and volume change during cycling hinders its practical application. Herein, we report an ingenious design of bio-inspired low-tortuosity carbon with tunable vertical micro-channels to be used as a host to incorporate nanosized Sn/Ni alloy nucleation sites, which can guide Li metal's plating/stripping and meanwhile accommodate the volume change. The pore sizes of the vertical channels of the carbon host can be regulated to investigate the structure–performance correlation. After compositing Li, the bio-inspired carbon host with the smallest pore size (∼14 μm) of vertical channels exhibits the lowest overpotential (∼18 mV at 1 mA cm−2), most stable tripping/plating voltage profiles, and best cycling stability (up to 500 cycles) in symmetrical cells. Notably, the carbon/Li composite anode is more rewarding than Li foil when coupled with LiFePO4 in full cells, exhibiting a much lower polarization effect, better rate capability and higher capacity retention (90.6% after 120 cycles). This novel bio-inspired design of a low-tortuosity carbon host with nanoalloy coatings may open a new avenue for fabricating advanced Li-metal batteries with high performance. [ABSTRACT FROM AUTHOR]

We herein demonstrate the ability of nitrogen heterocyclic ligands in connecting polyoxotitanium complexes into crystalline multiple cluster series. Moreover, their bandgap and photocatalytic water-splitting behavior were studied. The highest H2 evolution activity reaches up to 42.80 μmol g-1 h-1 for PTC-46. [ABSTRACT FROM AUTHOR]

Suitable electrocatalysts for industrial water splitting can veritably promote practical hydrogen applications. Guided by density functional theory calculations, the interface-rich Ni 2 P-NiSe 2 nanoparticles anchored on amorphous MoO x nanorods on nickel foam (Ni 2 P-NiSe 2 /MoO x /NF) are fabricated. Ni 2 P-NiSe 2 /MoO x /NF exhibits exceptional HER performance with overpotentials of 23 and 263 mV at 10 and 500 mA cm−2, outperforming most reported non-Pt based electrocatalysts reported hitherto. Remarkably, the excellent oxygen evolution activity (241 mV at 10 mA cm−2) of Ni 2 P-NiSe 2 /MoO x /NF further realizes the full electrolyzer requiring the voltage of 1.63 V at 50 mA cm−2 with robust stability (1000 h at 20 mA cm−2) in 1.0 M KOH. At industrial conditions (30% KOH, 65 °C), only 2.02 V is required to reach 1000 mA cm−2 with satisfying durability (200 h at 200 mA cm−2). When deployed in anion exchange membrane water electrolyzer, the catalyst achieves 1.3 A cm−2 at 2.7 V, associated with the prolonged stability. [Display omitted] • Electronic structure and localized charge density at Ni 2 P-NiSe 2 heterointerface are optimized when coupling with MoO 2. • Optimized heterointerfaces facilitated water/hydrogen adsorption and reduced energy barrier for water dissociation. • Fabricated Ni 2 P-NiSe 2 /MoO x /NF exhibited exceptional HER and OER performance under industrial conditions. • AEM water electrolyzer with Ni 2 P-NiSe 2 /MoO x /NF showed larger current density and prolonged stability. [ABSTRACT FROM AUTHOR]

The mesoporous Cd-Zn-S solid solutions (E-Cd x Zn 1-x S) with abundant surface defects synthesized via ingenious inorganic self-template co-precipitation method at room temperature, exhibiting high-efficient activity and stability for photocatalytic hydrogen evolution. The practical application of photocatalytic water splitting for hydrogen evolution hinges on the development of high-efficient and low-cost photocatalysts. Defects engineering has emerged as a promising strategy to enhance photocatalytic activity effectively. Herein, a facile and versatile co-precipitation method is proposed to fabricate mesoporous Cd-Zn-S solid solutions (E-Cd x Zn 1-x S) with abundant surface defects by the inorganic salts formed in the reaction system as self-template. Compared with Cd-Zn-S solid solutions (W-Cd 0.65 Zn 0.35 S) prepared by the traditional co-precipitation method, the enhanced specific surface area and abundant surface defects endow E-Cd 0.65 Zn 0.35 S with more accessible active sites and effective separation of electron-hole pairs for the photocatalytic water splitting reaction. The E-Cd 0.65 Zn 0.35 S solid solution exhibits hydrogen evolution rate of 5.2 mmol h−1 g−1 without loading noble metal as cocatalyst under visible light, which is 1.13 times higher than that of W-Cd 0.65 Zn 0.35 S sample. The present work provides a simple, low-cost and prospective strategy for the synthesis of defective Cd-Zn-S solid solutions, and it also delivers guidance to design and develop the advanced visible-light photocatalyst in the future. [ABSTRACT FROM AUTHOR]

[Display omitted] • NiFe LDH/phosphides are anchored on Co-NC nanorods array to form hierarchical open porous structure. • Synergistic effect between NiFe LDH/phosphides and Co-NC nanorods array can be achieved. • Co element can trigger the AEM and LOM dual reaction pathways to boost OER activity. • 240 mV and 137 mV at 100 mA cm−2 for OER and HER can be achieved with high stability. • Low operation potential of 1.579 V at 50 mA cm−2 for overall water splitting. The green hydrogen route provides a reliable way to reduce dependence on fossil fuels. Hydrogen production by water electrolysis is an efficient way to convert unstable renewable energy sources into hydrogen energy. Herein, a rod-like N-doped carbon nanorods array cooperated with layered double hydroxide (Ni 2 Fe@Co-NC/CC) and a tri-metal phosphides composite (P-Ni 2 Fe@Co-NC/CC) is fabricated, which is believed can facilitate the electron and mass transfer efficiency. The Co element in Ni 2 Fe@Co-NC/CC can promote the formation of high-valence Ni and activate lattice oxygen to form abundant dual OER active sites. While the P-Ni 2 Fe@Co-NC/CC can obtain optimized hydrogen adsorption free energy due to synergistic effect of trimetallic phosphides and nitrogen-doped carbon structure to promotes the HER progress. Therefore, due to the synergistic effect between metal hydroxide/phosphide and Co-decorated NC nanorods array, low overpotentials of 240 and 137 mV at 100 mA cm−2 can be achieved for OER and HER with excellent electrocatalytic stability. Besides, the Ni 2 Fe@Co-NC/CC//P-Ni 2 Fe@Co-NC/CC device can afford cell voltage of 1.579 V at 50 mA cm−2 in water splitting, which demonstrate a new idea for rational designed electrocatalytic water splitting composites towards high activity and stability. [ABSTRACT FROM AUTHOR]

Modulating electronic asymmetricity of catalysts is a novel option to regulate the electrocatalytic performance. Nevertheless, the efficient regulation of asymmetric degree of heterostructured catalysts at the atomic level still remains challenging. Herein, Ru nanoclusters (NCs, average particle size of ∼ 1.3 nm) were anchored on carbon materials doped by controllable N functional groups to optimize the electronic asymmetricity toward efficient hydrogen evolution reaction (HER). The electronic interaction between Ru and N species, and hence, the asymmetric electronic distribution of Ru NCs is subjectively manipulated by precisely tailoring the type of N dopants, especially pyrrolic-N, of carbon substrates. As a result, the pyrrolic-N dominated Ru-based heterostructures exhibit excellent HER activity compared to most of the current Ru-based electrocatalysts in basic media. Multiple spectroscopy experiments and density functional theory simulations demonstrate that the asymmetric distribution of surface electron of Ru-based heterostructures not only accelerates H 2 O adsorption and dissociation at interfacial Ru sites with positive charge but also facilitates the adsorption behavior of hydrogen on surface Ru sites with negative charge, thereby simultaneously optimizing the elementary steps in basic HER process. The present findings would provide some crucial understanding in manipulating the local electronic asymmetricity toward reasonable design and fabrication of advanced catalysts and beyond. [Display omitted] • Ru nanoclusters supported on N-doped carbon exhibits high performance for HER. • Electronic asymmetricity of Ru nanoclusters is manipulated by tailoring the type of N dopants. • Electronic asymmetry of Ru nanoclusters facilitates the formation of different active sites towards basic HER. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZIFs derived Ni-/Fe-/N- co-doped carbon on porous CoO nanowires array is fabricated. • The ZIFs can in-situ grown into the pores of CoO to increase interface robustness. • The open porous carbon with high hydrophilicity can promote mass transfer kinetics. • The rich metal-/N- active sites can accelerate OH− adsorption and reaction dynamics. • The composite reveals good OER performance with low overpotential and Tafel slope. Due to the sluggish four-electron transfer process, the oxygen evolution reaction (OER) kinetics should be speed up to achieve high energy conversion efficiency. The synergistic effect between transition metal heteroatoms and rational interface structural design can effectively enhance the electrocatalytic capability. Herein, utilizing the ZIFs as precursor, we fabricate a simple nickel-decorated three-dimensional Fe-/N- co-doped carbon continuously coated on porous cobalt oxide nanowires array. The partially immersion of carbon into porous CoO can form interlocked interface to enhance the structural stability. The vertically aligned N-doped carbon can facilitate the OH− adsorption, while the Ni-/Fe-/N- co-doped carbon on porous CoO can increase the active sites and enhance the intrinsic electrocatalytic capability. Therefore, the optimal electrode exhibits a low OER onset overpotential of 247.1 mV, low Tafel slope of 38.8 mV dec−1 and robust durability during 60 h test under alkaline condition. This work provides a new feasible strategy for rational structural design of advanced non-precious metal electrocatalysts. [ABSTRACT FROM AUTHOR]

FeNiP nanoparticles dispersed on carbon nanosheets were fabricated by direct pyrolysis, which achieved the improved electrochemical activities through optimizing Fe/Ni ratio. • FeNiP nanoparticles dispersed on N,P-doped carbon nanosheets fabricated by a facile method. • The electrochemical activity of the FeNiP/NPCS improved through optimizing Fe/Ni ratio. • High electrocatalytic activity and stability for HER, OER, and ORR. • High performance for overall water splitting and rechargeable Zn-air batteries. Hybridization of non-precious metals with advanced carbon monolith provides a promising approach to substitute noble metal catalysts for various electrochemical reactions. The structural and electronic properties of non-precious metals significantly affect electrocatalytic performance, which depends on the physicochemical structure of carbon substrates and the types of metal components. Herein, binary FeNi phosphide nanoparticles coupled with N,P-modified carbon nanosheets were fabricated through an universal carbonization-phosphorization approach. Besides the structural advantage of 2D nanosheets, the electronic structure change of bimetallic FeNi phosphides via modulating Fe/Ni ratio is another reason responded for the exceptional activities with reduced overpotentials of this hybridized catalyst for both hydrogen evolution, oxygen evolution and oxygen reduction reactions. Furthermore, by employing the fabricated materials as electrode catalysts for overall water splitting and rechargeable Zn-air batteries with liquid and solid-state electrolytes, excellent performances are achieved in these energy conversion and storage devices, revealing the significant feasibility for practical applications. [ABSTRACT FROM AUTHOR]