Water oxidation is the bottleneck reaction in artificial photosynthesis. Exploring highly active and stable molecular water oxidation catalysts (WOCs) is still a great challenge. In this study, a ...water‐soluble NiII complex bearing a redox non‐innocent tetraamido macrocyclic ligand (TAML) is found to be an efficient electrocatalyst for water oxidation in neutral potassium phosphate buffer. Controlled‐potential electrolysis experiments show that it can sustain at a steady current of approximately 0.2 mA cm−2 for >7 h at 1.75 V versus normal hydrogen electrode (NHE) without the formation of NiOx. Electrochemical and spectroelectrochemical tests show that the redox‐active ligand, as well as HPO42− in the buffer, participate in the catalytic cycle. More importantly, catalytically active intermediate NiIII(TAML2−)−O. is formed via several proton‐coupled electron transfer processes and reacts with H2O with the assistance of base to release molecular oxygen. Thus, the employment of redox non‐innocent ligands is a useful strategy for designing effective molecular WOCs.
Unblocking the bottleneck: Water oxidation is the bottleneck reaction in artificial photosynthesis. A water‐soluble NiII complex bearing a redox non‐innocent tetraamido macrocyclic ligand (TAML) is found to be an efficient electrocatalyst for water oxidation in neutral potassium phosphate buffer, sustaining a steady current of approximately 0.2 mA cm−2 for >7 h at 1.75 V versus the normal hydrogen electrode without the formation of NiOx.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Ion-solvating membranes have been gaining increasing attention as core components of electrochemical energy conversion and storage devices. However, the development of ion-solvating membranes with ...low ion resistance and high ion selectivity still poses challenges. In order to propose an effective strategy for high-performance ion-solvating membranes, this study conducted a comprehensive investigation on watermelon skin membranes through a combination of experimental research and molecular dynamics simulation. The micropores and continuous hydrogen-bonding networks constructed by the synergistic effect of cellulose fiber and pectin enable the hypodermis of watermelon skin membranes to have a high ion conductivity of 282.3 mS cm−1 (room temperature, saturated with 1 M KOH). The negatively charged groups and hydroxyl groups on the microporous channels increase the formate penetration resistance of watermelon skin membranes in contrast to commercially available membranes, and this is crucial for CO2 electroreduction. Therefore, the confinement of proton donors and negatively charged groups within three-dimensional microporous polymers gives inspiration for the design of high-performance ion-solvating membranes.The development of ion-solvating membranes with low ion resistance and high ion selectivity remains a challenge in the field of electrochemical energy conversion and storage. Here the authors report that watermelon skin ion-solvating membrane exhibits high ion conductivity and high ion selectivity.
Anion exchange membrane water electrolyzer (AEM‐WE) is a promising approach to producing green hydrogen using renewable energy. However, most of the reported AEM‐WEs still use platinum‐group ...metal‐based catalysts and the performance is far beyond unsatisfactory. Particularly, developing highly active, durable, and earth‐abundant metal‐based oxygen evolution reaction (OER) catalysts is essential to improve energy efficiency and reduce the costs of AEM‐WE. Herein, Ni2Fe8/Ni3S2/NF catalyst is fabricated in situ on nickel foam by a simple one‐pot hydrothermal reaction. The as‐prepared anode OER catalyst exhibits current densities of 500 and 1000 mA cm−2 at an overpotential (η) of 279 and 302 mV, superior to the performance of noble metal‐based catalysts (IrO2, RuO2). Coupled with Ni4Mo/MoO2/NF, the resulting single‐cell AEM‐WE displays high performance (1.65 V @ 1 A cm−2) and high durability (100 h @ 1 A cm−2), outperforming most of the reported AEM‐WEs assembled by non‐noble metal‐based catalysts. Additional characterization of the post‐test anode using different spectroscopic techniques further proved that the Ni2Fe8/Ni3S2/NF is a highly efficient and robust anode in the AEM‐WE device.
A low‐cost Ni2Fe8–Ni3S2/NF oxygen evolution reaction catalyst is developed as an anode material for anion exchange membrane water electrolyzer (AEM‐WE). The as‐prepared material displays high energy efficiency and device durability in AEM‐WE when coupled with Ni4Mo/MoO2/NF. The experimental results confirm that AEM‐WE equipped with platinum‐group metal‐free catalysts can achieve similar energy efficiency to proton exchange membrane‐WE.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A simple and low‐cost fabrication method is needed to obtain effective and robust heterogeneous catalysts for the oxygen evolution reaction (OER). In this study, an electrocatalyst FeNiOxHy with a ...hierarchical structure is synthesized on nickel foam by a simple fabrication method through anion exchange from a metal phosphate to a metal hydroxide. The as‐fabricated FeNiOxHy electrode requires overpotentials of 206 and 234 mV to deliver current densities of 10 and 50 mA cm−2, respectively. The catalytic performance of FeNiOxHy is superior to that of most previously reported FeNi‐based catalysts, including NiFe layered double hydroxide. The catalyst also shows good long‐term durability at a current density of 50 mA cm−2 over 50 h with no activity decay under 1 m KOH. By comparison to the directly electrodeposited FeNi hydroxide in morphology and electrochemical properties, the improved activity of the catalyst could be mainly attributed to an enhancement of its intrinsic activity, which was caused by the anion exchange of phosphate to (oxy)hydroxide. Further studies by cyclic voltammetry indicated a stronger interaction between Ni and Fe from the negative shift of the oxidation peak of Ni2+/Ni3+ in comparison with reported FeNiOxHy, which promoted the generation of active Ni3+ species more easily. This work may provide a new approach to the simple preparation of effective and robust OER catalysts by anion exchange.
State of the anion addressed: FeNiOxHy with a hierarchical structure is synthesized on nickel foam by a simple anion exchange method from a metal phosphate to a metal hydroxide and used as an electrocatalyst for the oxygen evolution reaction. The catalyst shows superior performance to most known FeNi‐based catalysts, including NiFe layered double hydroxide, and good long‐term durability
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A highly intrinsically active and optically transparent NiFeOxHy water oxidation catalyst was prepared by electrodeposition of Ni(C12‐tpen)(ClO4)2 complex (Ni−C12). This NiFeOxHy film has a current ...density of 10 mA cm−2 with an overpotential (η) of only 298 mV at nanomolar concentration and the current density of 10 mA cm−2 remains constant over 22 h in 1 m KOH. The extremely high turnover frequency of 0.51 s−1 was obtained with η of 300 mV. More importantly, such outstanding activity and transparency (optical loss <0.5 %) of the NiFeOxHy film are attributed to a ligand effect of the dodecyl substituent in Ni−C12, which enables its future application in solar water splitting.
The story of my NiFe: A highly intrinsically active and optically transparent NiFeOxHy water oxidation catalyst was prepared by electrodeposition of Ni(C12‐tpen)(ClO4)2 complex. This NiFeOxHy film has a current density of 10 mA cm−2 with an overpotential of only 298 mV at nanomolar concentration and the current density of 10 mA cm−2 remains constant over 22 h in 1 m KOH.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Water oxidation is currently believed to be the bottleneck in the field of electrochemical water splitting and artificial photosynthesis. Enormous efforts have been devoted toward the exploration of ...water oxidation catalysts (WOCs), including homogeneous and heterogeneous catalysts. Recently, Cu-based WOCs have been widely developed because of their high abundance, low cost, and biological relevance. However, to the best of our knowledge, no review has been made so far on such types of catalysts. Thus, we have summarized the recent progress made in the development of homogeneous and heterogeneous Cu-based WOCs for electrochemical catalysis. Furthermore, the evaluations of catalytic activity, stability, and mechanism of these catalysts are carefully concluded and highlighted. We believe that this review can summarize the current progress in the field of Cu-based electrochemical WOCs and help in the design of more efficient and stable WOCs.
The recent progress in the development of homogeneous and heterogeneous Cu-based WOCs for electrochemical catalysis.
Electricity‐driven organo‐oxidations have shown an increasing potential recently. However, oxygen evolution reaction (OER) is the primary competitive reaction, especially under high current ...densities, which leads to low Faradaic efficiency (FE) of the product and catalyst detachment from the electrode. Here, we report a bimetallic Ni−Cu electrocatalyst supported on Ni foam (Ni−Cu/NF) to passivate the OER process while the oxidation of 5‐hydroxymethylfurfural (HMF) is significantly enhanced. A current density of 1000 mA cm−2 can be achieved at 1.50 V vs. reversible hydrogen electrode, and both FE and yield keep close to 100 % over a wide range of potentials. Both experimental results and theoretical calculations reveal that Cu doping impedes the OH* deprotonation to O* and hereby OER process is greatly passivated. Those instructive results provide a new approach to realizing highly efficient biomass upgrading by regulating the OER activity.
A novel bimetallic Ni−Cu electrode for the oxidation of 5‐hydroxymethyl furfural (HMF) to 2,5‐furandicarboxylic acid (FDCA) with an industrial‐scale current density of up to 1000 mA cm−2 has been successfully developed. Superior stability and activity of the prepared electrode enable the gram‐scale production of FDCA with a very high overall yield, purity, and Faradaic efficiency.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Water oxidation is the bottleneck reaction in artificial photosynthesis. Exploring highly active and stable molecular water oxidation catalysts (WOCs) is still a great challenge. In this study, a ...water-soluble Ni
complex bearing a redox non-innocent tetraamido macrocyclic ligand (TAML) is found to be an efficient electrocatalyst for water oxidation in neutral potassium phosphate buffer. Controlled-potential electrolysis experiments show that it can sustain at a steady current of approximately 0.2 mA cm
for >7 h at 1.75 V versus normal hydrogen electrode (NHE) without the formation of NiO
. Electrochemical and spectroelectrochemical tests show that the redox-active ligand, as well as HPO
in the buffer, participate in the catalytic cycle. More importantly, catalytically active intermediate Ni
(TAML
)-O
is formed via several proton-coupled electron transfer processes and reacts with H
O with the assistance of base to release molecular oxygen. Thus, the employment of redox non-innocent ligands is a useful strategy for designing effective molecular WOCs.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The anion exchange membrane water electrolysis is widely regarded as the next‐generation technology for producing green hydrogen. The OH− conductivity of the anion exchange membrane plays a key role ...in the practical implementation of this device. Here, we present a series of Z−S‐x membranes with dibenzothiophene groups. These membranes contain sulfur‐enhanced hydrogen bond networks that link surrounding surface site hopping regions, forming continuous OH− conducting highways. Z−S‐20 has a high through‐plane OH− conductivity of 182±28 mS cm−1 and ultralong stability of 2650 h in KOH solution at 80 °C. Based on rational design, we achieved a high PGM‐free alkaline water electrolysis performance of 7.12 A cm−2 at 2.0 V in a flow cell and demonstrated durability of 650 h at 2 A cm−2 at 40 °C with a cell voltage increase of 0.65 mV/h.
With the introduction of dibenzothiophene into poly(aryl piperidinium) membrane, the sulfur‐enhanced hydrogen bond networks can efficiently transport the OH− ions through continuous OH− ions conducting highways, leading to significant improvement of anion exchange membrane water electrolysis.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
As a hole transporting material (HTM), N2,N2,N2′,N2′,N7,N7,N7′,N7′-octakis (4-methoxyphenyl) spiro fluorene-9,9′-xanthene-2,2′,7,7′-tetraamine (X60) in mesoscopic perovskite solar cells (PSCs) has ...been widely utilized for substitution of the 2,2′,7,7′-tetrakis (N,N-di-p-methoxyphenylamine)-9,9′-spiro-bi-fluorene (spiro-OMeTAD). In this study, we have introduced an ionic liquid N-butyl-N'-(4-pyridylheptyl) imidazolium bis (trifluoromethane) sulfonamide (BuPyIm-TFSI) as a p-dopant to increase the hole conductivity and stability of the X60 based perovskite solar cells. As a result, based on the different concentrations of BuPyIm-TFSI in mesoscopic PSCs, the optimal condition (4.85 mM) showed the best power conversion efficiency (PCE) of 14.65%, which is extremely higher than the device without BuPyIm-TFSI. Moreover, the device based on X60: BuPyIm-TFSI composite HTM at ambient conditions with humidity of ~40% exhibited good PSCs performance with the long-term stability of 840 h. Hence, the use of BuPyIm-TFSI as a p-dopant for X60 played a significant role in enhancing the electrical properties, stability and efficiency of PSCs.
•The highest PCE of 14.65% of PSC achieved at a concentration of 4.85 mM of BuPyIm-TFSI.•X60: BuPyIm-TFSI hole transporting material enhanced the stability of PSC devices over 840 h at 40 RH.•Maintain higher than 93% PCE over 840 h at ~40 RH under ambient condition.•The Voc, Jsc, FF, and PCE increase with the increase of concentrations of BuPyIm-TFSI.•New curve of HTM absorbance is observed at 525 nm after doping of X60 with BuPyIm-TFSI, related to the oxidation of X60.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
