Pt‑Based Intermetallic Compound Catalysts for the Oxygen Reduction Reaction:Structural Control at the Atomic Scale to Achieve a Win–Win Situation Between Catalytic Activity and Stability

The development of ordered Pt-based intermetallic compounds is an effective way to optimize the electronic characteristics of Pt and its disordered alloys,inhibit the loss of transition metal elements,and prepare fuel cell catalysts with high activity and long-term durability for the oxygen reduction reaction(ORR).This paper reviews the structure–activity characteristics,research advances,problems,and improvements in Pt-based intermetallic compound fuel cell catalysts for the ORR.First,the structural characteristics and performance advantages of Pt-based intermetallic compounds are analyzed and explained.Second,starting with 3d transition metals such as Fe,Co,and Ni,whose research achievements are common,the preparation process and properties of Pt-based intermetallic compound catalysts for the ORR are introduced in detail according to element types.Third,in view of preparation problems,improvements in the preparation processes of Pt-based intermetallic compounds are also summarized in regard to four aspects:coating to control the crystal size,doping to promote ordering transformation,constructing a“Pt skin”to improve performance,and anchoring and confinement to enhance the interaction between the crystal and support.Finally,by analyzing the research status of Pt-based intermetallic compound catalysts for the ORR,prospective research directions are suggested.

High performance octahedral PtNi/C catalysts investigated from rotating disk electrode to membrane electrode assembly

Octahedral PtNi/C catalysts have demonstrated superior catalytic performance in oxyge n reduction reacti on (ORR) over commercial Pt/C with rotating disk electrode (RDE). However, it is not trivial to translate such promising results to real-world membrane-electrode assembly (MEA). In this work, we have synthesized octahedral PtNi/C catalysts using poly(diallyldimethylammonium chloride)(PDDA) as a capping age nt and in vestigated their performance from RDE to MEA. In RDE, mass activity and specific activity of the optimized octahedral PtNi/C catalyst for oxygen reduction reaction (ORR) are nearly 19 and 28 times high of the state-of-the-art commercial Pt/C, respectively. At MEA level, the octahedral PtNi/C catalyst exhibits excelle nt power generation performa nee and durability paired with commercial Pt/C ano de. Its cell voltage at 1,000mA·cm^-2 reaches 0.712 V, and maximum power density is 881.6 mW·cm^-2 and its performance attenuation is also less, around 11.8% and 7% under galvanostatic condition of 1,000 mA·cm^-2 for 100 h. Such results are investiaged by thermodynamic analysis and fundametal performance modeling, which indicate the single cell performance can be further improved by reducing the size of PtNi/C catalyst agglomerates. Such encouraging results have demonstrated the feasibility to convey the superior performance of octahedral PtNi/C from RDE to MEA.

The Controllable Design of Catalyst Inks to Enhance PEMFC Performance:A Review

Typical catalyst inks in proton exchange membrane fuel cells(PEMFCs)are composed of a catalyst,its support,an ionomer and a solvent and are used with solution processing approaches to manufacture conventional catalyst layers(CLs).Because of this,catalyst ink formulation and deposition processes are closely related to CL structure and performance.However,catalyst inks with ideal rheology and optimized electrochemical performances remain lacking in the large-scale application of PEMFCs.To address this,this review will summarize current progress in the formulation,characterization,modeling and deposition of catalyst inks.In addition,this review will highlight recent advancements in catalyst ink materials and discuss corresponding complex interactions.This review will also present various catalyst ink dispersion methods with insights into their stability and introduce the application of small-angle scattering and cryogenic transmission electron microscopy(cryo-TEM)technologies in the characterization of catalyst ink microstructures.Finally,recent studies in the kinetic modeling and deposition of catalyst inks will be analyzed.

Modifying Carbon Supports of Catalyst for the Oxygen Reduction Reaction in Vehicle PEMFCs

For current carbon-supported Pt catalysts in vehicle proton exchange membrane fuel cells(PEMFCs),the insufficient stability and durability of carbon supports are severe limitations under operating conditions.This paper adopts the accelerated stress test(AST)method to study the carbon corrosion of catalysts,which is significant to efficiently select the catalysts supports in fuel cells.Graphitized carbon blacks with various surface properties are heated under different conditions,followed by evaluation of their antioxidation capacity with the AST.It is shown that optimally graphitized carbon blacks demonstrate superior stability,retaining a constant quinone/hydroquinone(QH)transition peak potential for over 70,000 AST cycles.A Pt catalyst supported on the selected graphitized carbon exhibits excellent durability at both the rotating disk electrode(RDE)and membrane electrode assembly(MEA)levels.The final specific mass activity(MA)of the optimum catalyst is 47.87 mA/mgPt,which is 2.06 times that of commercial Pt/C(23.31 mA/mgPt)in the RDE tests.The final maximum power density of the optimum catalyst is 525.68 mW/cm^(2),which is 305.52 mW/cm^(2)higher than that of commercial Pt/C after undergoing the AST during the MEA measurements.These results prove that the rational surface features of carbon supports play a vital role in improving the overall fuel cell performance by realizing uniform dispersion of Pt nanoparticles,resisting corrosion,and reinforcing metal-support interactions.