Kinetically Accelerating Elementary Steps via Bridged Ru-H State for the Hydrogen-Evolution in Anion-Exchange Membrane Electrolyzer

Designing hydrogen evolution reaction (HER) electrocatalysts for facilitating its sluggish adsorption kinetics is crucial in generating green hydrogen via sustainable water electrolysis. Herein, a high-performance ultra-low Ruthenium (Ru) catalyst is developed consisting of atomically-layered Ru nanoclusters with adjacent single Ru sites, which executs a bridging-Ru-H activation strategy to kinetically accelerate the HER elementary steps. Owing to its optimal electronic structure and unique adsorption configuration, the hybrid Ru catalyst simultaneously displayed a drastically reduced overpotential of 16 mV at 10 mA cm⁻² as well as a low Tafel slope of 35.2 mV dec⁻¹ in alkaline electrolyte. When further coupled with a commercial IrO₂ anode catalyst, the ensembled anion-exchange membrane water electrolyzer achievs a current density of 1.0 A cm⁻² at a voltage of only 1.70 V_cell. In situ spectroscopic analysis verified that Ru single atom and atomically-layered Ru nanoclusters in the hybrid materials play a critical role in facilitating water dissociation and weakening *H adsorption, respectively. Theoretical calculations further elucidate the underlaying mechanism, suggesting that the dissociated proton at the single atom Ru site orients itself adjacently with Ru nanoclusters in a bridged structure through targeted charge transfer, thus promoting Volmer-Heyrovsky dynamics and boosting the HER activity.     

PEM water electrolysis: Innovative approaches towards catalyst separation,recovery and recycling

We report the development of a facile recycling process for catalyst coated membranes (CCMs) used in polymer electrolyte membrane (PEM) water electrolyzers. After performance evaluation in an assembled electrolysis cell, ultrasonication is used to provide high-yield recovery of not only the noble-metal catalyst materials, but also of the fluoropolymer membrane itself, without the release of hazardous gases. Transmission electron microscopy (TEM) and electrochemical characterization are used to confirm the retention of catalyst particle size, and of the performance of the recycled CCMs. Furthermore, our projections indicate that, if this approach is widely employed, existing resources of noble metals will prove sufficient for the gigawatt-scale implementation of PEM water electrolyzers. This has profound implications for the achievement of current targets for reducing the consumption of precious metals for applications in electrolyzers, fuel cells and other energy storage devices.     

Performance evaluation of a solarized gas turbine system integrated to a high temperature electrolyzer for hydrogen production

In this paper, the performance of a solar gas turbine (SGT) system integrated to a high temperature electrolyzer (HTE) to generate hybrid electrical power and hydrogen fuel is analyzed. The idea behind this design is to mitigate the losses in the electrical power transmission and use the enthalpy of exhaust gases released from the gas turbine (GT) to make steam for the HTE. In this context, a GT system is coupled with a solar tower including heliostat solar field and central receiver to generate electrical power. To make steam for the HTE, a flameless boiler is integrated to the SGT system applying the SGT extremely high temperature exhaust gases as the oxidizer. The results indicate that by increasing the solar receiver outlet temperature from 800 K to 1300 K, the solar share increases from 22.1% to 42.38% and the overall fuel consumption of the plant reduces from 7 kg/s to 2.7 kg/s. Furthermore, flameless mode is achievable in the boiler while the turbine inlet temperature (TIT) is maintained at the temperatures higher than 1314 K. Using constant amounts of the SGT electrical power, the HTE voltage decreases by enhancing the HTE steam temperature which result in the augmentation of the overall hydrogen production. To increase the HTE steam temperature from 950 K to 1350 K, the rate of fuel consumption in the flameless boiler increases from 0.1 m/s to 0.8 m/s; however, since the HTE hydrogen production increases from 4.24 mol/s to 16 mol/s it can be interpreted that the higher steam temperatures would be affordable. The presented hybrid system in this paper can be employed to perform more thermochemical analyses to achieve insightful understanding of the hybrid electrical power-hydrogen production systems.     

Understanding the Role of (W,Mo, Sb) Dopants in the Catalyst Evolution and Activity Enhancement of Co3O4 during Water Electrolysis via In Situ Spectroelectrochemical Techniques

Unlocking the potential of the hydrogen economy is dependent on achieving green hydrogen (H₂) production at competitive costs. Engineering highly active and durable catalysts for both oxygen and hydrogen evolution reactions (OER and HER) from earth-abundant elements is key to decreasing costs of electrolysis, a carbon-free route for H₂ production. Here, a scalable strategy to prepare doped cobalt oxide (Co₃O₄) electrocatalysts with ultralow loading, disclosing the role of tungsten (W), molybdenum (Mo), and antimony (Sb) dopants in enhancing OER/HER activity in alkaline conditions, is reported. In situ Raman and X-ray absorption spectroscopies, and electrochemical measurements demonstrate that the dopants do not alter the reaction mechanisms but increase the bulk conductivity and density of redox active sites. As a result, the W-doped Co₃O₄ electrode requires ≈390 and ≈560 mV overpotentials to reach ±10 and ±100 mA cm⁻² for OER and HER, respectively, over long-term electrolysis. Furthermore, optimal Mo-doping leads to the highest OER and HER activities of 8524 and 634 A g⁻¹ at overpotentials of 0.67 and 0.45 V, respectively. These novel insights provide directions for the effective engineering of Co₃O₄ as a low-cost material for green hydrogen electrocatalysis at large scales.     

Asymmetric Active Sites for Boosting Oxygen Evolution Reaction

Transition metal-nitrogen-carbon materials with atomically dispersed active sites are promising catalysts for oxygen evolution reaction (OER) since they combine the strengths of both homogeneous and heterogeneous catalysts. However, the canonically symmetric active site usually exhibits poor OER intrinsic activity due to its excessively strong or weak oxygen species adsorption. Here, a catalyst with asymmetric MN₄ sites based on the 3-s-triazine of g-C₃N₄ (termed as a-MN₄@NC) is proposed. Compared to symmetric, the asymmetric active sites directly modulate the oxygen species adsorption via unifying planar and axial orbitals (dx²-y², dz²), thus enabling higher OER intrinsic activity. In Silico screening suggested that cobalt has the best OER activity among familiar nonprecious transition metal. These experimental results suggest that the intrinsic activity of asymmetric active sites (179 mV overpotential at onset potential) is enhanced by 48.4% compared to symmetric under similar conditions. Remarkably, a-CoN₄@NC showed excellent activity in alkaline water electrolyzer (AWE) device as OER catalyst, the electrolyzer only required 1.7 V and 2.1 V respectively to reach the current density of 150 mA cm⁻² and 500 mA cm⁻². This work opens an avenue for modulating the active sites to obtain high intrinsic electrocatalytic performance including, but not limited to, OER.     

Activity-Stability Balance: The Role of Electron Supply Effect of Support in Acidic Oxygen Evolution

Developing efficient and durable electrocatalysts for the oxygen evolution reaction (OER) in proton exchange membrane (PEM) electrolyzers represents a significant challenge. Herein, the cobalt-ruthenium oxide nano-heterostructures are successfully synthesized on carbon cloth (CoO_x/RuO_x-CC) for acidic OER through a simple and fast solution combustion strategy. The rapid oxidation process endows CoO_x/RuO_x-CC with abundant interfacial sites and defect structures, which enhances the number of active sites and the charge transfer at the electrolyte-catalyst interface, promoting the OER kinetics. Moreover, the electron supply effect of the CoO_x support allows electrons to transfer from Co to Ru sites during the OER process, which is beneficial to alleviate the ion leaching and over-oxidation of Ru sites, improving the catalyst activity and stability. As a self-supported electrocatalyst, CoO_x/RuO_x-CC displays an ultralow overpotential of 180 mV at 10 mA cm⁻² for OER. Notably, the PEM electrolyzer using CoO_x/RuO_x-CC as the anode can be operated at 100 mA cm⁻² stably for 100 h. Mechanistic analysis shows that the strong catalyst-support interaction is beneficial to redistribute the electronic structure of Ru O bond to weaken its covalency, thereby optimizing the binding energy of OER intermediates and lowering the reaction energy barrier.     

离子膜电解槽运行中几个常见问题的简述

在离子膜法电解生产氮碱过程中，影响电槽运行的因素有：进槽盐水质量、高纯盐酸质量、去离子水纯度、阴、阳极液浓度、电槽温度、压差波动等。只有严格工艺管理，保证工艺指标，才能使电解装置长期、稳定、高效运行。     

Fabrication of platinum thin films for ultra-high electrocatalytic hydrogen evolution reaction

While the noble metals (e.g., platinum, (Pt)) remain the benchmark electrocatalyst for the hydrogen evolution reaction (HER), their mass production require a reduced metal loading and faster fabrication protocols. The aim of the present work is to prepare Pt thin films by simple and fast fabrication technique, and to evaluate their performance for HER. The thin films of Pt are grown on two substrates, namely titanium foil (Ti) and nickel foam (NF), using a single step aerosol assisted chemical vapor deposition (AACVD) method. The film deposition time are varied from 20 to 60 min. Microscopic analyses suggest a gradual evolution of the films into percolated and/or porous nanostructures, a feature that remains highly desired to allow the maximum access of active sites. The performance of the as-prepared electrodes is evaluated by monitoring the HER in acidic electrolyte. The Pt film on nickel foam (Pt/NF) exhibits better electrical conductivity and smaller charge transfer resistance, while the film deposited on the Ti foil (Pt/Ti) demonstrates superior catalytic activity per active sites. The as-prepared Pt/Ti and Pt/NF electrodes produce 10 mA cm⁻² at overpotential of 28 mV and 26 mV, respectively, better in performance than commercial Pt/C electrode (~39 mV), set a new bench mark electrocatalyst for the HER.     

M (Co,Ni), N and S tridoped carbon nanoplates as multifunctional catalysts for rechargeable Zn-air batteries and water electrolyzers

Exploration of multifunctional non-precious metal catalysts towards oxygen reduction reaction (ORR), oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is very important for many clean energy technologies. Here, two trifunctional catalysts based on M (Co, Ni), N and S tridoped carbon nanoplates (Co/N/S-CNPs and Ni/N/S-CNPs) are reported. Due to the relatively higher catalytic site content, graphitization degree and smaller charge-transfer resistance, the Co/N/S-CNPs catalyst shows higher activity and stability for ORR (onset potential of 0.99 V and half-wave potential of 0.87 V vs. RHE (reversible hydrogen electrode)), OER (overpotential at 10 mA cm^?2 of 0.37 V) and HER than the Ni/N/S-CNPs catalyst. Furthermore, when constructed with the Co/N/S-CNPs and commercial 20 wt% Pt/C + Ir/C cathodes, respectively, Zn-air battery (ZnAB) based on the Co/N/S-CNPs cathode displays better performance, including a higher power density of 96.0 mW cm^?2 and cycling stability at 5 mA cm^?2. In addition, an alkaline electrolyzer assembled with the Co/N/S-CNPs catalyst as a bifunctional catalyst can reach 10 mA cm^?2 at 1.65 V for overall water splitting and maintain excellent stability even after cycling for 12 h. The present work proves the potential of the Co/N/S-CNPs catalyst for many clean energy devices.