Tuning the Electrochemical Properties of Polymeric Cobalt Phthalocyanines for Efficient Water Splitting

Polymeric metal phthalocyanines have great potential as electrocatalysts, yet their incorporation on a current collector without losing the activity of metal centers remains a challenge. Herein, a new strategy for preparing a series of polymeric cobalt phthalocyanines containing S linkers (pCoPc-1) or SO₂ linkers (pCoPc-2) and their tunable electrochemical properties are reported. The pCoPcs coated on various substrates show favorable electrocatalytic activities toward oxygen and hydrogen evolution reactions (OER and HER). Particularly, the pCoPc-1 layer on Co₃O₄ nanosheet arrays exerts a cooperative effect enhancing both the OER and HER performances, and the subsequent phosphorization (P@pCoPc-1/Co₃O₄|CC) significantly boosts the HER performance with enhanced hydrophilicity and conductivity. The high permeability and stability reinforcement of the pCoPc-1 layer allow the phosphorization of underlying Co₃O₄ to CoP without degradation, which remarkably enhances OER and HER performances as manifested by low overpotentials of 320 and 120 mV at 10 mA cm⁻², respectively. When engaged as a bifunctional electrocatalyst for the overall water splitting, the P@pCoPc-1/Co₃O₄|CC requires a low cell voltage of 1.672 V at 10 mA cm⁻², showing long-term durability and mechanical robustness. This study demonstrates the collaborative catalytic role of polymeric macrocyclic compounds that offers versatile tunability and stability for various electrocatalytic reactions.     

Ru-Pincer Complex-Bridged Cu-Porphyrin Polymer for Robust (Photo)Electrocatalytic H2 Evolution via Single-Atom Active Sites

Organic polymers have attracted much attention in the field of energy conversion owing to their excellent tailoring ability via heterometal incorporation and/or functionalization. Herein, a novel pincer complex-bridged porphyrin polymer is synthesized using Cu-porphyrin (CuPor) and Ru-N′NN′-pincer complex (RuN₃) as monomers. The resultant CuPor-RuN₃ polymer delivers robust electrocatalytic hydrogen evolution reaction (HER) performance with outstanding durability and ultralow overpotentials of 73 and 114 mV at a current density of 10 mA cm^-2 in acidic and alkaline media, respectively. Moreover, the CuPor-RuN₃ polymer displays great potential to fabricate photoelectrochemical (PEC) cells with a BiVO₄ photoanode, where the additional photoinduced electrons from CuPor-RuN₃ endow the BiVO₄||CuPor-RuN₃ PEC cell with much better activity for overall water splitting than the BiVO₄||Pt/C one, demonstrating that CuPor-RuN₃ would be a promising (photo)electrocatalyst to replace the benchmark Pt/C. The experimental and theoretical studies reveal that the Cu/Ru heterobimetallic centers in the polymer not only enhance the inherent electron transfer from Cu sites to Ru ones that serve as single-atom catalytic sites (Ru-N₃), but also efficiently regulate the electronic property of the Ru-N₃ sites, and thus boosting (photo)electrocatalytic HER activity. The proposed strategy opens a new avenue to fabricate porphyrin-based polymers with heteromultimetallic centers as effective HER (photo)electrocatalysts.     

Dual‐Phase Engineering of Nickel Boride‐Hydroxide Nanoparticles toward High‐Performance Water Oxidation Electrocatalysts

The development of earth‐abundant and efficient oxygen evolution reaction (OER) electrocatalysts is necessary for green hydrogen production. The preparation of efficient OER electrocatalysts requires both the adsorption sites and charge transfer on the catalyst surface to be suitably engineered. Herein, the design of an electrocatalyst is reported with significantly enhanced water oxidation performance via dual‐phase engineering, which displays a high number of adsorption sites and facile charge transfer. More importantly, a simple chemical etching process enables the formation of a highly metallic transition boride phase in conjunction with the transition metal hydroxide phase with abundant adsorption sites available for the intermediates formed in the OER. In addition, computational simulations are carried out to demonstrate the water oxidation mechanism and the real active sites in this engineered material. This research provides a new material design strategy for the preparation of high‐performance OER electrocatalysts.     

Non-platinum cathode catalyst layer composition for single Membrane Electrode Assembly Proton Exchange Membrane Fuel Cell

The performance of nano-structured templated non-platinum-based cathode electrocatalysts for proton exchange membrane fuel cells (PEMFC) was evaluated for different catalyst layer compositions. The effect of non-platinum catalyst, Nafion, and 35 wt% Teflon modified Vulcan XC-72 Carbon Blacks (XC-35) loadings were measured under H₂/air and H₂/O₂ conditions. Transport hindrances that occur in the catalyst layers are evaluated with ΔE vs. i analysis. It is shown that transport limitations in the cathode catalyst layer can limit the performance of the cell at relatively low current densities if the catalyst layer composition is not optimized. Further, a procedure is outlined here to aid in the implementation of non-traditional catalyst materials into fuel cell systems (i.e. templated electrocatalyst as compared to the standard supported material).     

Investigation of PdNiO/C catalyst for methanol electrooxidation

The methanol electrooxidation reaction was studied on carbon dispersed Pd-nickel oxide nanocatalysts in KOH/CH₃OH solutions. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize PdNiO/C catalysts. The electrochemical behaviors for the methanol electrooxidation reaction were measured in a powder microelectrode by cyclic voltammetry and Tafel plots. The result showed that the adding NiO enhances the anti-poison ability of PdNiO/C catalyst, but the reaction mechanism does not change. The anti-poison ability of PdNiO/C catalyst can be enhanced by three ways: (1) the NiOOH on the surface of catalyst improves the activity of composite catalyst for methanol oxidation; (2) the catalytic role of NiO for methanol dehydration; (3) the promotion of large amount active species-PdO (low oxidation state) for methanol oxidation.     

Synthesis of La0.6Ca0.4Co0.8Ir0.2O3 perovskite for bi-functional catalysis in an alkaline electrolyte

The amorphous citrate precursor method was employed to prepare perovskite of La_0.6Ca_0.4Co_0.8Ir_0.2O₃ as a bi-functional electrocatalyst for oxygen reduction and evolution in an alkaline electrolyte. The X-ray diffraction pattern of the as-synthesized powders exhibited a majority phase identical to that of La_0.6Ca_0.4CoO₃, indicating successful incorporation of Ir⁴⁺ at the Co cation sites. Scanning Electron Microscope images demonstrated a foam-like microstructure with a surface area of 13.31 m² g⁻¹. For electrochemical characterization, the La_0.6Ca_0.4Co_0.8Ir_0.2O₃ particles were supported on carbon nanocapsules (CNCs) and deposited on commercially available gas diffusion electrodes with a loading of 2.4 mg cm⁻². In current–potential polarizations, La_0.6Ca_0.4Co_0.8Ir_0.2O₃/CNCs revealed more enhanced bi-functional catalytic abilities than La_0.6Ca_0.4CoO₃/CNCs. Similar behaviors were observed in galvanostatic profiles for oxygen reduction and evolution at current densities of 50 and 100 mA cm⁻² for 10 min. Moreover, notable changes from zeta potential measurements were recorded for La_0.6Ca_0.4Co_0.8Ir_0.2O₃ relative to La_0.6Ca_0.4CoO₃. In lifetime determinations, where a repeated 3 h sequence of oxygen reduction/resting/oxygen evolution/resting was imposed, La_0.6Ca_0.4Co_0.8Ir_0.2O₃/CNCs delivered a stable and sustainable behavior with moderate degradation.     

A cobalt polypyrrole composite catalyzed cathode for the direct borohydride fuel cell

A cobalt polypyrrole carbon (Co-PPY-C) composite has been attempted for use as a cathode catalyst in a direct borohydride fuel cell (DBFC). A Co-PPY-C composite has been fabricated in laboratory and characterized by the field emission scanning electron microscopy, transmission electron microscopy, as well as X-ray photoemission spectroscopy. Fabricated Co-PPY-C catalyst demonstrates good short-term durability and activity which are comparable to those obtained from the Pt/C catalyst. A maximum power density of 65 mW cm⁻² has been achieved at ambient conditions. This research concludes that metallo-organic coordination compounds would be potential candidates for use as cathode catalysts in the DBFC.     

Boosting CO tolerance and stability of Pt electrocatalyst supported on sulfonated carbon nanotubes

CO tolerance and stability are of prominent importance for the anodic electrocatalyst utilized in direct methanol fuel cells (DMFCs). Due to the electrochemical instability of Ru atoms, the state-of-the-art DMFC anodic electrocatalyst (PtRu/C) is unable to survive for long time. Here, we report a newly designed Pt electrocatalyst with robust CO tolerance and stability after coating with poly(vinyl pyrrolidone) (PVP). Electrochemically active surface area (ESA) is negligibly affected by the PVP decoration; meanwhile, almost undetectable ESA loss is obtained for the PVP decorated Pt electrocatalyst. However, the ESA degradations for non-decorated and commercial CB/Pt electrocatalysts are found to be 30% and 40%, respectively. The improved stability is ascribed to the strong interaction between PVP and sulfonated carbon nanotubes. Also, the CO tolerance evaluated from the methanol oxidation reaction is ∼3 and 3.5 fold higher compared to non-decorated and commercial CB/Pt electrocatalysts, respectively, which is attributed to the hydrophilic PVP polymer accelerating the water absorption and formation of Pt(OH)_ads species to re-activate nearby CO poisoned Pt nanoparticles. Thus, decoration with PVP polymer can simultaneously promote the stability and CO anti-poisoning of Pt electrocatalyst.     

电解水制氢MoS2催化剂研究与氢能技术展望

氢气具有质量轻、热值高、燃烧产物清洁等优点,被认为是理想的能源载体。氢气既能作为燃料电池的燃料,又能作为储能介质调节风能、太阳能发电系统的随机性、间歇性,正在成为未来能源的重要组成部分。为了促进电解水制氢技术与装备发展,研究高效电催化剂十分重要。本文围绕“粉末型”与“自支撑型”电催化剂结构特征,讨论基于二硫化钼（MoS₂）的析氢电催化剂的研究现状,阐述了催化活性位点调控策略与提高导电性两条技术途径,并以析氢过电位和塔菲尔曲线斜率为依据,比较不同方法制备的二硫化钼电催化剂的催化活性。表明提高二硫化钼晶相稳定性、调节其电子结构和优化催化电极结构等方法,将进一步提高基于二硫化钼的析氢催化电极性能。     

微波辅助合成纳米SnO2及其在乙醇电催化中的应用

以水合氯化亚锡、乙二醇和水为原料,常压下经微波加热制备了粒径均匀的纳米SnO2颗粒,并将其应用到催化剂Pt-SnO2/C中。通过XRD和TEM对制备的SnO2颗粒和催化剂的微观结构进行表征,结果表明,微波辅助合成的SnO2为四方晶相,大小约为2.0nm,粒径均一。循环伏安和计时电流测试表明Pt-SnO2/C比商业化催化剂具有更高的乙醇催化氧化活性。