Electrocatalytically Active Graphene supported MMo Carbides (M Ni, Co) for Oxygen Reduction Reaction

Cerium-Based Electrocatalysts for Oxygen Evolution/Reduction Reactions: Progress and Perspectives

Ce-based materials have been widely used in photocatalysis and other fields because of their rich redox pairs and oxygen vacancies, despite research on the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) remaining scare. However, most pristine cerium-based materials, such as CeO₂, are non-conductive materials. Therefore, how to obtain highly conductive and stable OER/ORR electrocatalysts is currently a hot research topic. To overcome these limitations, researchers have proposed a variety of strategies to promote the development of Ce-based electrocatalysts in recent years. This progress report focuses on reviewing new strategies concerning three categories of Ce-based electrocatalysts: metal-organic framework (MOF) derivatives, structure tuning, and polymetallic doping. It also puts forward the main existing problems and future prospects. The content of cerium in the crust is about 0.0046%, which is the highest among the rare earth elements. As a low-cost rare earth material, Ce-based materials have a bright future in the field of electrocatalysis due to replacing precious metal and some transition metals.

Facile synthesis of N-doped graphene supported porous cobalt molybdenum oxynitride nanodendrites for the oxygen reduction reaction

Exploring an inexpensive, active and stable electrocatalyst as an alternative to expensive Pt for the oxygen reduction reaction (ORR), porous Co-Mo-ON alloy nanodendrites supported on nitrogen-doped graphene (Co-Mo-ON/NG) have been synthesized by a two-step solid state heating method. The Co-Mo-ON/NG nanodendrites offer high ORR activity and superior electrochemical stability both in acidic and alkaline media. This superiority is due to the synergistic effect of NG, enhanced catalytic efficiency by Mo, highly active intrinsic surface area and exposure of catalytic facets of nanodendritic morphology towards the ORR. The Co-Mo-ON/NG nanodendrites show a 4e- ORR process with 0.710 V and 0.915 V onset potentials in 0.5 M H2SO4 and 0.1 M KOH, respectively. The Co-Mo-ON/NG nanodendrites show extreme electrochemical stability in terms of 96% and 97% current retention for 40 000 s in both acidic and alkaline media, respectively, long term durability for continuous 2000 cycles and greater resistance to methanol than the commercial Pt/C catalyst. Furthermore, Mo-ON/NG, Co-ON/NG, and Co-Mo-ON are also tested to evaluate the effect of Mo-doping and NG on the electrocatalytic activity of Co-Mo-ON/NG nanodendrites. Owing to their low cost, easy synthesis, outstanding ORR performance, and extreme durability, Co-Mo-ON/NG nanodendrites emerged as a promising non-precious and highly stable ORR electrocatalyst in fuel cell applications.

High-performance Platinum-free oxygen reduction reaction and hydrogen oxidation reaction catalyst in polymer electrolyte membrane fuel cell

The integration of polymer electrolyte membrane fuel cell (PEMFC) stack into vehicles necessitates the replacement of high-priced platinum (Pt)-based electrocatalyst, which contributes to about 45% of the cost of the stack. The implementation of high-performance and durable Pt metal-free catalyst for both oxygen reduction reaction (ORR) and hydrogen oxidation reaction (HOR) could significantly enable large-scale commercialization of fuel cell–powered vehicles. Towards this goal, a simple, scalable, single-step synthesis method was adopted to develop palladium-cobalt alloy supported on nitrogen-doped reduced graphene oxide (Pd₃Co/NG) nanocomposite. Rotating ring-disk electrode (RRDE) studies for the electrochemical activity towards ORR indicates that ORR proceeds via nearly four-electron mechanism. Besides, the mass activity of Pd₃Co/NG shows an enhancement of 1.6 times compared to that of Pd/NG. The full fuel cell measurements were carried out using Pd₃Co/NG at the anode, cathode in conjunction with Pt/C and simultaneously at both anode and cathode. A maximum power density of 68 mW/cm² is accomplished from the simultaneous use of Pd₃Co/NG as both anode and cathode electrocatalyst with individual loading of 0.5 mg/cm² at 60 °C without any backpressure. To the best of our knowledge, the present study is the first of its kind of a fully non-Pt based PEM full cell.

Three-dimensional supramolecular phosphomolybdate architecture-derived Mo-based electrocatalytic system for overall water splitting

With phosphomolybdate supramolecular architecture-derived Mo₂C@NC and MoO₂@NC as cathode and anode, an efficient electrolyzer was constructed, which possessed excellent overall water splitting activity.