https://onlinelibrary.wiley.com/doi/pdf/10.1002/adfm.202003261

Bifunctional Heterostructured Transition Metal Phosphides for Efficient Electrochemical Water Splitting

ConspectusHydrogen is an ideal energy carrier and plays a critical role in the future energy transition. Distinct from steam reforming, electrochemical water splitting, especially powered by renewa...

Synergistic Modulation of Non-Precious-Metal Electrocatalysts for Advanced Water Splitting.

Rational design of single atom catalyst is critical for efficient sustainable energy conversion. However, the atomic-level control of active sites is essential for electrocatalytic materials in alkaline electrolyte. Moreover, well-defined surface structures lead to in-depth understanding of catalytic mechanisms. Herein, we report a single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets (Ru1/D-NiFe LDH). Under precise regulation of local coordination environments of catalytically active sites and the existence of the defects, Ru1/D-NiFe LDH delivers an ultralow overpotential of 18 mV at 10 mA cm−2 for hydrogen evolution reaction, surpassing the commercial Pt/C catalyst. Density functional theory calculations reveal that Ru1/D-NiFe LDH optimizes the adsorption energies of intermediates for hydrogen evolution reaction and promotes the O–O coupling at a Ru–O active site for oxygen evolution reaction. The Ru1/D-NiFe LDH as an ideal model reveals superior water splitting performance with potential for the development of promising water-alkali electrocatalysts. Rational design of single atom catalyst is critical for efficient sustainable energy conversion. Single-atomic-site ruthenium stabilized on defective nickel-iron layered double hydroxide nanosheets achieve superior HER and OER performance in alkaline media.

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Engineering single-atomic ruthenium catalytic sites on defective nickel-iron layered double hydroxide for overall water splitting.

Electronic Redistribution: Construction and Modulation of Interface Engineering on CoP for Enhancing Overall Water Splitting

The lithium-ion exchange rate capability of various commercial graphite materials are evaluated using galvanostatic charge/discharge cycling in a half-cell configuration over a wide range of C-rates (0.1 similar to 60C). The results confirm that graphite is capable of de-intercalating stored charge at high rates, but has a poor intercalating rate capability. Decreasing the graphite coating thickness leads to a limited rate performance improvement of the electrode. Reducing the graphite particle size shows enhanced C-rate capability but with increased irreversible capacity loss (ICL). It is demonstrated that the rate of intercalation of lithium-ions into the graphite is significantly limited compared with the corresponding rate of de-intercalation at high C-rates. For the successful utilisation of commercially available conventional graphite as a negative electrode in a lithium-ion capacitor (LIC), its intercalation rate capability needs to be improved or oversized to accommodate high charge rates.

Rate capability of graphite materials as negative electrodes in lithium-ion capacitors

The modulation of electron density is an effective option for efficient alternative electrocatalysts. Here, p-n junctions are constructed in 3D free-standing FeNi-LDH/CoP/carbon cloth (CC) electrode (LDH=layered double hydroxide). The positively charged FeNi-LDH in the space-charge region can significantly boost oxygen evolution reaction. Therefore, the j at 1.485 V (vs. RHE) of FeNi-LDH/CoP/CC achieves ca. 10-fold and ca. 100-fold increases compared to those of FeNi-LDH/CC and CoP/CC, respectively. Density functional theory calculation reveals OH- has a stronger trend to adsorb on the surface of FeNi-LDH side in the p-n junction compared to individual FeNi-LDH further verifying the synergistic effect in the p-n junction. Additionally, it represents excellent activity toward water splitting. The utilization of heterojunctions would open up an entirely new possibility to purposefully regulate the electronic structure of active sites and promote their catalytic activities.

Utilizing the Space-Charge Region of the FeNi-LDH/CoP p-n Junction to Promote Performance in Oxygen Evolution Electrocatalysis.

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. However, their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. Here, CoS2/CoS heterojunction nanoparticles with uneven charge distribution, which are synthesized in situ on graphite felt by a one-step solvothermal process, can significantly boost electrocatalytic activities of I−/I3− and S2−/Sx2− redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS2/CoS heterojunction can deliver a high energy efficiency of 84.5% at a current density of 10 mA cm−2, a power density of 86.2 mW cm−2 and a stable energy efficiency retention of 96% after approximately 1000 h of continuous operation. Polysulfide/iodide redox flow batteries are promising due to low cost and high-solubility components, but are limited by energy efficiency and power density. Here the authors fabricate heterojunction electrocatalysts to achieve improved performance in a polysulfide/iodide redox flow battery.

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Highly active nanostructured CoS 2 /CoS heterojunction electrocatalysts for aqueous polysulfide/iodide redox flow batteries.

Fabrication of multi-doped catalysts generally involves complex and energy-intensive processes including the preparation of special precursor, solvent evaporation, and post separation or treatment. Herein, we have developed an eco-friendly one-step process to effectively regulate the electronic structure of products by combining the concepts of alloy, heteroatoms doping, phase controlling and heterostructures. The obtained CoFe and Co2P nanoparticles encapsulated in multi-doped nanoporous carbon (NPSC-Co2Fe1) exhibits a small potential gap between Ej=10 and E1/2 of 0.75 V for bifunctional electrocatalytic O2 redox reactions. It is revealed that defect-rich multi-doped carbon-based nanoarchitecture and electronic redistribution provide more donor-acceptor active sites with reduced energy barrier. Notably, ZABs using NPSC-Co2Fe1 as air electrodes exhibit outstanding charge-discharge performances and cycling stability superior to those of ZABs with Pt/C-IrO2. The flexible all-solid-state ZABs with NPSC-Co2Fe1 operate stably even under bending state. Moreover, these batteries are implemented to power mini-fans and LED panels.

One-step construction of multi-doped nanoporous carbon-based nanoarchitecture as an advanced bifunctional oxygen electrode for Zn-Air batteries

Fe doping promoted electrocatalytic N2 reduction reaction of 2H MoS2

Aqueous polysulfide/iodide redox flow batteries (RFBs) are an attractive candidate for scalable energy storage with highly soluble active materials, which show great potential to reduce RFB cost. However, their energy efficiency is usually limited by poor kinetics reversibility and electrochemical activity of the redox reaction of polysulfide couples on the graphite felt electrode, which hinder its further practical applications. Here, Cu2XGeS4 (X = Fe, Co, Ni, Cd, Mn) nanocrystals are successfully synthesized through the hot injection method, and then uniformly coated onto the surface of graphite felt as electrodes. These electrodes can successfully suppress the water splitting side reactions, especially the hydrogen evolution reaction. The ones with Cu2CoGeS4 nanocrystals can significantly boost electrocatalytic activities of S2−/Sx2− redox reactions for the proper adsorbability of polysulfide, which inturn improve the charge transfer process and selectively facilitate the electro-conversion reactions of polysulfides. Furthermore, the polysulfide/iodide flow battery with GF–Cu2CoGeS4 generates a high energy efficiency of 77.2% at 20 mA cm−2, a power density of 40.7 mW cm−2 and a stable energy efficiency retention of 92% after approximately 250 continuous cycles.

Cu2CoGeS4 nanocrystals for high performance aqueous polysulfide/iodide redox flow batteries: enhanced selectively towards the electrocatalytic conversion of polysulfides

Tsegaye Tadesse Tsega

Papers

Utilizing the Space-Charge Region of the FeNi-LDH/CoP p-n Junction to Promote Performance in Oxygen Evolution Electrocatalysis.

Highly active nanostructured CoS 2 /CoS heterojunction electrocatalysts for aqueous polysulfide/iodide redox flow batteries.

One-step construction of multi-doped nanoporous carbon-based nanoarchitecture as an advanced bifunctional oxygen electrode for Zn-Air batteries

Fe doping promoted electrocatalytic N2 reduction reaction of 2H MoS2

Cu2CoGeS4 nanocrystals for high performance aqueous polysulfide/iodide redox flow batteries: enhanced selectively towards the electrocatalytic conversion of polysulfides