Improving Alkaline Hydrogen Oxidation through Dynamic Lattice Hydrogen Migration in Pd@Pt Core-Shell Electrocatalysts

Tracking the trajectory of hydrogen intermediates during hydrogen electro-catalysis is beneficial for designing synergetic multi-component catalysts with division of chemical labor. Herein, we demonstrate a novel dynamic lattice hydrogen (LH) migration mechanism that leads to two orders of magnitude increase in the alkaline hydrogen oxidation reaction (HOR) activity on Pd@Pt over pure Pd, even ≈31.8 times mass activity enhancement than commercial Pt. Specifically, the polarization-driven electrochemical hydrogenation process from Pd@Pt to PdH_x@Pt by incorporating LH allows more surface vacancy Pt sites to increase the surface H coverage. The inverse dehydrogenation process makes PdH_x as an H reservoir, providing LH migrates to the surface of Pt and participates in the HOR. Meanwhile, the formation of PdH_x induces electronic effect, lowering the energy barrier of rate-determining Volmer step, thus resulting in the HOR kinetics on Pd@Pt being proportional to the LH concentration in the in situ formed PdH_x@Pt. Moreover, this dynamic catalysis mechanism would open up the catalysts scope for hydrogen electro-catalysis.     

Boosting Alkaline Hydrogen Evolution Reaction through Water Structure Manipulation

In the past, the design of efficient electrocatalyst materials for alkaline hydrogen evolution reaction (HER) was mostly focused on tuning the adsorption properties of reaction intermediates. A recent breakthrough shows that the performance can be improved by manipulating water structure at the electrode-electrolyte interface using atomically localized electric fields. The new approach was realized by using IrRu dizygotic single-atom sites and led to a significantly accelerated water dissociation and an overall improved alkaline HER performance. Supported by extensive data from advanced modeling, characterization, and electrochemical measurements, the work delivers an intricate examination of the interaction between water molecules and the catalyst surface, thereby enriching our understanding of water dissociation kinetics and offering new insights to boost overall alkaline HER efficiency.     

Interfacial Engineering of Ni/V2O3 Heterostructure Catalyst for Boosting Hydrogen Oxidation Reaction in Alkaline Electrolytes

Alkaline fuel cells can permit the adoption of platinum group metal-free (PGM-free) catalysts and cheap bipolar plates, thus further lowering the cost. With the exploration of PGM-free hydrogen oxidation reaction (HOR) catalysts, nickel-based compounds have been considered as the most promising HOR catalysts in alkali. Here we report an interfacial engineering through the formation of nickel-vanadium oxide (Ni/V₂O₃) heterostructures to activate Ni for efficient HOR catalysis in alkali. The strong electron transfer from Ni to V₂O₃ could modulate the electronic structure of Ni sites. The optimal Ni/V₂O₃ catalyst exhibits a high intrinsic activity of 0.038 mA cm⁻² and outstanding stability. Experimental and theoretical studies reveal that Ni/V₂O₃ interface as the active sites can enable to optimize the hydrogen and hydroxyl bindings, as well as protect metallic Ni from extensive oxidation, thus achieving the notable activity and durability.     

Pb-Modified Ultrathin RuCu Nanoflowers for Active,Stable, and CO-resistant Alkaline Electrocatalytic Hydrogen Oxidation

CO poisoning of Pt group metal (PGM) catalysts is a chronic problem for hydrogen oxidation reaction (HOR), the anodic reaction of hydroxide exchange membrane fuel cell (HEMFC) for converting H₂ to electric energy in sustainable manner. We demonstrate here an ultrathin Ru-based nanoflower modified with Pb (PbRuCu NF) as an active, stable, and CO-resistant catalyst for alkaline HOR. Mechanism studies show that the presence of Pb can weaken the adsorption of *H, strengthen *OH adsorption to facilitate CO oxidation, as a result of significantly enhanced HOR activity and improved CO tolerance. Furthermore, in situ electrochemical attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) suggests that Pb acts as oxygen-rich site to regulate the behavior of the linear CO adsorption. The optimized Pb_1.04-Ru₉₂Cu₈/C displays a mass activity and specific activity of 1.10 A mg_Ru⁻¹ and 5.55 mA cm⁻², which are ≈10 and ≈31 times higher than those of commercial Pt/C. This work provides a facile strategy for the design of Ru-based catalyst with high activity and strong CO-resistance for alkaline HOR, which may promote the fundamental researches on the rational design of functional catalysts.     

Breaking Surface Atomic Monogeneity of Rh2P Nanocatalysts by Defect-Derived Phosphorus Vacancies for Efficient Alkaline Hydrogen Oxidation

Breaking atomic monogeneity of catalyst surfaces is promising for constructing synergistic active centers to cope with complex multi-step catalytic reactions. Here, we report a defect-derived strategy for creating surface phosphorous vacancies (P-vacancies) on nanometric Rh₂P electrocatalysts toward drastically boosted electrocatalysis for alkaline hydrogen oxidation reaction (HOR). This strategy disrupts the monogeneity and atomic regularity of the thermodynamically stable P-terminated surfaces. Density functional theory calculations initially verify that the competitive adsorption behavior of H_ad and OH_ad on perfect P-terminated Rh₂P{200} facets (p-Rh₂P) can be bypassed on defective Rh₂P{200} surfaces (d-Rh₂P). The P-vacancies enable the exposure of sub-surface Rh atoms to act as exclusive H adsorption sites. Therein, the H_ad cooperates with the OH_ad on the peripheral P-sites to effectively accelerate the alkaline HOR. Defective Rh₂P nanowires (d-Rh₂P NWs) and perfect Rh₂P nanocubes (p-Rh₂P NCs) are then elaborately synthesized to experimentally represent the d-Rh₂P and p-Rh₂P catalytic surfaces. As expected, the P-vacancy-enriched d-Rh₂P NWs catalyst exhibits extremely high catalytic activity and outstanding CO tolerance for alkaline HOR electrocatalysis, attaining 5.7 and 14.3 times mass activity that of p-Rh₂P NCs and commercial Pt/C, respectively. This work sheds light on breaking the surface atomic monogeneity for the development of efficient heterogeneous catalysts.     

Stabilizing Low-Valence Single Atoms by Constructing Metalloid Tungsten Carbide Supports for Efficient Hydrogen Oxidation and Evolution

Designing novel single-atom catalysts (SACs) supports to modulate the electronic structure is crucial to optimize the catalytic activity, but rather challenging. Herein, a general strategy is proposed to utilize the metalloid properties of supports to trap and stabilize single-atoms with low-valence states. A series of single-atoms supported on the surface of tungsten carbide (M-WC_x, M=Ru, Ir, Pd) are rationally developed through a facile pyrolysis method. Benefiting from the metalloid properties of WC_x, the single-atoms exhibit weak coordination with surface W and C atoms, resulting in the formation of low-valence active centers similar to metals. The unique metal-metal interaction effectively stabilizes the low-valence single atoms on the WC_x surface and improves the electronic orbital energy level distribution of the active sites. As expected, the representative Ru-WC_x exhibits superior mass activities of 7.84 and 62.52 A mg_Ru⁻¹ for the hydrogen oxidation and evolution reactions (HOR/HER), respectively. In-depth mechanistic analysis demonstrates that an ideal dual-sites cooperative mechanism achieves a suitable adsorption balance of H_ad and OH_ad, resulting in an energetically favorable Volmer step. This work offers new guidance for the precise construction of highly active SACs.     

The Role of Discrepant Reactive Intermediates on Ru-Ru2P Heterostructure for pH-Universal Hydrogen Oxidation Reaction

Developing highly efficient electrocatalysts for hydrogen oxidation reaction (HOR) under alkaline media is essential for the commercialization of alkaline exchange membrane fuel cell (AEMFC). However, the kinetics of HOR in alkaline media is complicated, resulting in orders of magnitude slower than that in acid, even for the state-of-the-art Pt/C. Here, we find that Ru-Ru₂P/C heterostructure shows HOR performance with a non-monotonous variation in a whole pH region. Unexpectedly, an inflection point located at pH≈7 is observed, showing an anomalous behavior that HOR activity under alkaline media surpasses acidic media. Combining experimental results and theoretical calculations, we propose the roles of discrepant reactive intermediates for pH-universal HOR, while H* and H₂O* adsorption strengths are responsible for acidic HOR, and OH* adsorption strength is essential for alkaline HOR. This work not only sheds light on fundamentally understanding the mechanism of HOR but also provides new designing principles for pH-targeted electrocatalysts.     

Thermodynamic and Kinetic Studies on Oxidation of Pyrogallol Red by Hydrogen Peroxide in the Absence and Presence of Molybdenum(VI)

Abstract

The oxidation of pyrogallol red (PGR) by hydrogen peroxide has been studied both in the absence and presence of molybdenum(VI) at pH of 7.0 by spectrophotometric detection. The reaction rate was studied with a fix-time method from 0.5 to 4.5 min. The effect of reagents concentration, ionic strength and temperature was studied to give the optimum conditions. At the optimizing conditions the rate constant, energy and entropy of activation and frequency factor have been calculated using the Arrhenius and Eyring plots.     

Remarkably Enhanced Hydrogen Oxidation Reaction Activity of Carbon-supported Pt by Facile Nickel Modification

Developing high activity catalysts for hydrogen oxidation reaction(HOR)under alkaline condition remains a challenge in the exchange membrane fuel cell(AEMFC).Herein,we report that the activity of carbon-supported platinum(Pt/C)towards the hydrogen oxidation reaction(HOR)in alkaline media can be remarkably enhanced by simple immersion of Pt/C in nickel chloride solution.The adsorption of hydrogen on the catalyst surface is weakened by modification of nickel.The HOR activity on the Pt/C after immersion possesses an excellent mass current density of 33.4 A/gmetal,which is 18%higher than that(28.3 A/gmetal)on Pt/C.     

Electrocatalytic Oxidation of Hydrogen Peroxide on Poly(m‐toluidine)‐Nickel Modified Carbon Paste Electrode in Alkaline Medium

The poly(m‐toluidine) film was prepared by using the repeated potential cycling technique in an acidic solution at the surface of carbon paste electrode. Then transition metal ions of Ni(II) were incorporated to the polymer by immersion of the modified electrode in a 0.2 M NiSO₄, also the electrochemical characterization of this modified electrode exhibits stable redox behavior of the Ni(III)/Ni(II) couple. The electrocatalytic ability of Ni(II)/poly(m‐toluidine)/modified carbon paste electrode (Ni/PMT/MCPE) was demonstrated by electrocatalytic oxidation of hydrogen peroxide with cyclic voltammetry and chronoamperometry methods in the alkaline solution. The effects of scan rate and hydrogen peroxide concentration on the anodic peak height of hydrogen peroxide oxidation were also investigated. The catalytic oxidation peak current showed two linear ranges with different slopes dependent on the hydrogen peroxide concentration and the lower detection limit was 6.5 μM (S/N=3). The catalytic reaction rate constant, (k_h), was calculated 5.5×10² M^?1 s^?1 by the data of chronoamperometry. This modified electrode has many advantages such as simple preparation procedure, good reproducibility and high catalytic activity toward the hydrogen peroxide oxidation. This method was also applied as a simple method for routine control and can be employed directly without any pretreatment or separation for analysis cosmetics products.     

纳络酮对氯化铝导致的小鼠学习记忆障碍及血中锌铜锰含量变？…

通过口服氯化建立小鼠学习记忆障碍模型,在此模型的基础上用跳台法观察了纳络酮对铝中毒小鼠学习记忆障碍的改善作用,并采用火焰原子吸收分光光度法测定了小鼠血中锌,铜,锰的含量。结果显示,氯化铝可导致小习学生记忆障碍,且降低血中Ｚｎ、Ｃｕ含量（Ｐ〈０．０５）,而纳络酮有改善铝中毒小鼠学习记忆障碍的作用,同时也增加了血中Ｚｎ、Ｃｕ含量。     

The Influencing of Preanodized Inlaying Ultrathin Carbon Paste Electrode on the Oxidation for the Xanthine and Hypoxanthine by the Hydrogen Bond

In this paper, a pre‐anodized inlaying ultrathin carbon paste electrode (PAIUCPE) with 316L as a matrix was constructed by a simple and fast electrochemical pretreatment. Using xanthine (Xa) and hypoxanthine (HXa) as the target compounds, the pH effects compositions of buffer solution, the accumulation times, hydrogen bond catalysis, degree of auxiliary electrode reaction on the size of peak currents (I_p) of Xa and HXa was discussed in detail. Also, it was proposed that Xa and HXa were respectively absorbed at the surface of PAIUCPE through hydrogen bonding. The influencing mechanisms of the PAIUCEP on electrochemical oxidation of Xa and HXa were explained in detail. Moreover, the linear relationships for the Xa and HXa were obtained in the range of 6×10^?8–3×10^?5 mol/L and 2×10^?7–7×10^?5 mol/L, respectively. The detection limits for the Xa and HXa were 1.2×10^?8 mol/L and 5.7×10^?8 mol/L, respectively. Moreover, this proposed method could be applied to determine the Xa and HXa in human urine simultaneously with satisfactory results.     

Back Cover: Multilayered Ceramic Membrane with Ion Conducting Thin Layer Induced by Interface Reaction for Stable Hydrogen Production (Angew. Chem. Int. Ed. 6/2023)

Conventional methods for fabricating multilayered ceramic membranes with ion conducting dense thin layers are often cumbersome, costly, and limited by poor adhesion between layers. Inspired by the architectural structure of the rooted grasses in soil, here, we report an interface-reaction-induced reassembly approach for the direct fabrication of Ce_0.9Gd_0.1O_2−δ (CGO) thin layers rooted in the parent multilayered ceramic membranes by only one firing step. The CGO dense layers are very thin, and adhered strongly to the parent support layer, ensuring low ionic transport resistance and structural integrity of the multilayered membranes. When using as an oxygen permeable membrane for upgrading fossil-fuel-derived hydrogen, it shows very long durability in harsh conditions containing H₂O, CH₄, H₂, CO₂ and H₂S. Furthermore, our approach is highly scalable and applicable to a wide variety of ion conducting thin layers, including Y_0.08Zr_0.92O_2−δ, Ce_0.9Sm_0.1O_2−δ and Ce_0.9Pr_0.1O_2−δ.