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Pt–Ni nanoparticles (NPs) are used as electrocatalysts toward the oxygen reduction reaction due to their high mass activity. However, degradation processes at high potential under the acidic conditions of proton exchange membrane fuel cells delay their massive implementation. The model presented here facilitates understanding of the corrosion by clearing variables related to the electrochemical measurement (non-equilibrium conditions and complex system) and focusing on the gradual etching of Ni via two-phase Ni(II) transfer treatment promoted by chelating agents (CAs). We synthesized Pt–Ni/C octahedral NPs and then used six chemically different CAs as corrosion agents for Ni. The corrosion yielded concave octahedral and hexapod NPs. Amine-rich CA treatment results in particle detachment from the carbon substrates, while carboxylic-rich CA treatment preserves the carbon–particle bond. We correlate the detachment to the type of chemical group in the CAs and the Ni etching is correlated to the pH. The ORR of the best catalyst is reported.

Catalyst poisoning is a prominent issue, reducing the lifetime of catalysts and increasing the costs of the processes that rely on them. The electrocatalysts that enable green energy conversion and storage, such as proton exchange membrane fuel cells and hydrogen bromine redox flow batteries, also suffer from this issue, hindering their utilization. Current solutions to protect electrocatalysts from harmful species fall short of effective selectivity without inhibiting the required reactions. This article describes the protection of a standard 50% Pt/C catalyst with a V2O5 coating through atomic layer deposition (ALD). The ALD selectively deposited V2O5 on the Pt, which enhanced hydrogen transport to the Pt surface and resulted in a higher mass activity in alkaline electrolytes. Cyclic voltammetry and X-ray photoelectron spectroscopy showed that the Pt was protected by the coating in the HBr/Br2 electrolyte which dissolved the uncoated 50% Pt/C in under 3 min.

The oxygen evolution reaction (OER) is an essential reaction for the sustainable synthesis of fuels from renewable feedstocks. In recent years, cathode materials for Li-ion batteries have been succ...

International audience; PtNi is amongst the most active electrocatalyst for the oxygen reduction reaction, but its stability in operation is uncertain. Intuitively, alkaline environments lead to milder degradations than acidic ones, although carbon-supported Pt-group metal nanoparticles are particularly degraded even in dilute alkaline electrolytes. To date, PtNi catalysts durability has not been characterized for alkaline oxygen reduction and evolution reactions (ORR and OER). Herein, carbon-supported shape controlled PtNi catalysts were compared in terms of activity and durability during alkaline ORR and OER. The PtNi catalysts are shape-controlled Pt-rich alloy, Ni-rich alloy, and Pt core/Ni shell (Pt@Ni) synthesized on Vulcan XC72R carbon. Their morphology and composition were evaluated by identical-location transmission electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction pre and post accelerated stress test. Compared to Pt/C and Ni/C benchmark catalysts, the core-shell and Ni-rich alloy catalysts gave high and stable OER activities. After accelerated stress test, the catalysts show two features which are believed to play a major role in the durability: a Ni-enrichment at the nanoparticles' surface and an improved attachment of the catalyst to the carbon support.

LiNi0.8Co0.1Mn0.1O2 (NCM811) is a promising cathode material for long range electric vehicles. However, the material suffers severe chemo-mechanical degradation that can cause gradual capacity loss upon prolonged cycling. Surface passivation of NMC811 was demonstrated to help in retaining the structural integrity of the material upon extended cycling. Herein, we report the surface passivation of the NCM811 using Li2S and Na2S precursors via direct and simple wet chemical treatment, for the mitigation of parasitic reactions at the electrode electrolyte interphase. This phenomenon is accompanied by increase in the oxidation state of sulfur (from sulfide to sulfate) and partial reduction in the oxidation state of nickel. Electrochemical performance measurements show that the M2SO4 (M: Li, Na) protection layer on NMC811 behaves as an artificial cathode electrolyte interphase (ACEI) that enhance the capacity retention by 25% during prolong cycling with respect to the untreated NMC811. Postmortem morphology studies reveal that the thin metal sulfates coatings remain on the cathode even after 100 cycles, while the untreated NCM811 shows severe morphological instabilities. Our study demonstrates that by simple chemical treatment of NMC811 can enhance its overall stability and cycling performance for the development of advanced high energy density Lithium-ion battery systems.

The hydrogen-bromineredox flow battery's(H2Br2RFB) advantages of high energy capacity, highround-tripconversion efficiency and low cost, make it an optimal candidate for large-scaleenergy storagesystems. The crossover ofbromidespecies through the membrane degrades the performance of the H2Br2RFB by poisoning the catalyst responsible for thehydrogen evolutionand oxidation reactions. Herein we propose the new concept of a selective catalystcoating layerthat mitigates the effect of bromide crossover. The polymerization ofdopamineon thecatalyst surfaceyields ananoscaleconformal polydopamine layer which acts as a semi-permeable barrier to block bromide species. The H2Br2RFB with the coated catalyst shows a low capacity fading of 6% at 300 mA cm−2after exposure to 4.5 M charged electrolyte for 2 h. Even the beginning of lifepolarizationcurves show the benefit of catalyst coating with a high peak power of ∼550 mW cm−2. Hence, the catalyst coating opens a way to solve the crossover issue in H2Br2RFB technology.