High‐Performance Oxygen Reduction Electrocatalysis Enabled by 3D PdNi Nanocorals with Hierarchical Porosity

Abstract

including sustainable fuel cells and next-generation metal-air batteries. [1][2][3][4][5][6] Unfortunately, the complex reaction pathways and intrinsically sluggish reaction kinetics of the ORR predominantly limit the overall efficiency of energy conversion. Although platinum (Pt) and its alloys have been recognized as the most efficient ORR electrocatalysts to date, some critical issues, including the ever-increasing cost, scarce reserve, fuel crossover, and unsatisfactory durability of Pt, pose a severe challenge toward the widespread commercialization for these electrochemical energy devices. [7][8][9][10][11][12] In this regard, it is of great significance and highly imperative to explore Pt-free alternative electrocatalysts with superior activity and excellent durability, as well as low cost. Fortunately, the less expensive and more abundant palladium (Pd) nanostructures represent a class of promising and reliable ORR electrocatalysts with comparable or even superior electrocatalytic performances than Pt-based catalysts. [13][14][15][16][17][18][19] Moreover, incorporation of Pd with a secondary earth-abundant 3d-transition metal (TM) to form Pd-TM bimetallic alloy can not only further reduce the consumption of precious Pd, but also effectively modify the electronic structure of Pd, which often leads to extraordinary electrocatalytic properties, such as enhanced superior activity, high selectivity, and sufficient stability, which are inaccessible by the monometallic counterparts or physical mixture. [14,15,20,21] Among various 3d-transition metals, Ni has been identified as a promising candidate to form Pd-Ni alloys with excellent catalytic performances due to its relatively cheap price and the elaborate synergy between Ni and Pd. [14,[22][23][24] As such, PdNi bimetallic nanoalloys are considered to be a highly economical and efficient ORR electrocatalyst.On the other hand, construction of 3D networked nanostructures with hierarchical porosity, i.e., mesopores connected with macropores, also provides an effective strategy to improve the utilization efficiency of noble metal atoms and structural robustness of a noble metal-based nanocatalyst. Such unique structural feature could endow the catalyst with several fantastic properties which are distinct from the solid counterparts, including high surface area, low density, metallic backbone, excellent molecular accessibility, minimized mass diffusive Cost-effective electrocatalysts for the oxygen reduction reaction (ORR) play pivotal roles in energy conversion and storage processes. Designing a 3D networked bimetallic nanostructure with hierarchical porosity represents a reliable and effective strategy for the advancement of electrocatalysts with greatly improved activity and stability. However, it still remains a tremendous challenge in fabricating such fantastic nanostructure via a feasible and economical approach. Herein, a facile cyanogel-bridged synthetic strategy is demonstrated to fabricate PdNi 3D nanocorals with hierarchical porosity. The elaborate inte...

Cyanogel-Derived Synthesis of Porous PdFe Nanohydrangeas as Electrocatalysts for Oxygen Reduction Reaction

“…Moreover, doping an earth-abundant 3d-transition metal M (M = Ni, Co, Cu, Fe, etc.) into Pd to form Pd-M bimetallic alloys can not only further reduce the use of expensive Pd but also tune the electronic structure of Pd effectively, which always results in excellent electrocatalytic performance [13][14][15][16]. For instance, Bharali's group prepared carbon-supported PdNi electrocatalysts, which have remarkable ORR and formic acid oxidation behavior [17].…”

Porous Noble Metal Electrocatalysts: Synthesis, Performance, and Development

“…Noble metal-containing precipitates, e.g., coordination polymers, [76] oxides, [77] and phosphates, [78] with desirable structure and morphology can be utilized as self-template. In a typical synthetic process, removal of excess component or region by reducing or etching would bring about the final porous noble metal, and the specific removal method determines the density of the product.…”

“…Pt-based alloys and Pd-based alloys exhibit relatively excellent catalytic performance in acidic and basic ORR, and further introduction of nonnoble metals (such as Cu, Ni) can reduce the amount of noble metal while maintaining or even optimizing electrocatalytic performance (Table 4). [22,38,76] In addition to forming alloy with metals, nonmetals are also viable alternative choice. For instance, PdBP mesoporous nanospheres synthesized by soft template method with dimethylamine borane and NaH 2 PO 2 as boron and phosphorus source exhibit improved electrocatalytic performance.…”

“…Pd nanodandelion [100] 0.1 m KOH 5 255 10.9 (9.3) 863 (832) --Pd 3 Pb nanowires network [127] 0. PdNi nanocoral [76] 0.1 m KOH 5 255 18.9 (6.3) 851 (837) -0.014 at 0.85 V (0.009) PdBP mesoporous nanosphere [63] 0.1 m KOH 10 42 59.1 (41.1) 920 34.8 1.45 at 0.9 V (0.49)…”

Chemical Design of Palladium‐Based Nanoarchitectures for Catalytic Applications

“…To date, numerous Pd‐based intermetallics and alloys have been reported in the literature . Table 1 lists an exhaustive summary of previously reported Pd‐based alloys and intermetallics, including their synthetic approach, application, and properties.…”