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

Abstract

It is important to develop cost-efficient electrocatalysts used in the oxygen reduction reaction (ORR) for widespread applications in fuel cells. Palladium (Pd) is a promising catalyst, due to its more abundant reserves and lower price than platinum (Pt), and doping an earth-abundant 3d-transition metal M into Pd to form Pd–M bimetallic alloys may not only further reduce the use of expensive Pd but also promote the electrocatalytic performance of ORR, owing to the synergistic effect between Pd and M. Here we report a cyanogel-derived synthesis of PdFe alloys with porous nanostructure via a simple coinstantaneous reduction reaction by using K2PdIICl4/K4FeII(CN)6 cyanogel as precursor. The synthesized PdFe alloys possess hydrangea-like morphology and porous nanostructure, which are beneficial to the electrochemical performance in ORR. The onset potential of the porous PdFe nanohydrangeas is determined to be 0.988 V, which is much more positive than that of commercial Pt/C catalyst (0.976 V) and Pd black catalyst (0.964 V). Resulting from the unique structural advantages and synergetic effect between bimetals, the synthesized PdFe nanohydrangeas with porous structure have outstanding electrocatalytic activity and stability for ORR, compared with the commercial Pd black and Pt/C.

Cyanogel‐Induced PdCu Alloy with Pd‐Enriched Surface for Formic Acid Oxidation and Oxygen Reduction

“…Cyanogel, formed by the repeated coordination of metal ion and cyanogroup (M-CN-M', M ¼ Fe, Co, Ni, Pd, Pt), can be used as ideal precursors for noble metal-based alloy catalysts with 3D structures. [45,46] Cyanogel reduction has several unique merits: i) The preparation process is simple and the gelling conditions are not limited by air humidity, temperature and pressure for catalysts. [47,48] ii) Uniform distribution of metal ions at the atomic scale in cyanogel facilitates the formation of alloy phases.…”

“…[50] Moreover, NaBH 4 , as a strong reducing agent, can rapidly reduce Pd and Cu ions to achieve the formation of PdCu alloy. [45] At present, the reported Pd-based cyanogels include Pd [45][46][47]51] The lack of research on PdCu cyanogel may be largely attributed to the instability of K 2 [Cu(CN) 4 ], which easily decomposes to copper (I) cyanide and releases toxic cyanide gas at room temperature (2CuðCNÞ 2À 4 ! ðCNÞ 2 þ 2CuðCNÞ 2À 3 ), thus limiting the formation of PdCu alloy.…”

“…[ 50 ] Moreover, NaBH 4 , as a strong reducing agent, can rapidly reduce Pd and Cu ions to achieve the formation of PdCu alloy. [ 45 ] At present, the reported Pd‐based cyanogels include Pd x [Ni(CN) 4 ] y ·aH 2 O, Pd x [Fe(CN) 6 ] y ·aH 2 O, and Pd x [Co(CN) 6 ] y ·aH 2 O, which are used to synthesize PdNi, PdFe and PdCo alloy, respectively, but there is no concern about PdCu cyanogel. [ 45–47,51 ] The lack of research on PdCu cyanogel may be largely attributed to the instability of K 2 [Cu(CN) 4 ], which easily decomposes to copper (I) cyanide and releases toxic cyanide gas at room temperature (), thus limiting the formation of PdCu alloy.…”

Ordered intermetallic compounds combining precious metals and transition metals for electrocatalysis

“…Due to its small impact on the environment, high power density, and high energy conversion efficiency, it is increasingly favored by researchers. ( Gao et al, 2020 ; He et al, 2020 ; Prithi et al, 2021 ; Wan et al, 2021 ; Kurdin et al, 2022 ; Liu et al, 2022 ) However, it is limited by the expensive cost of Pt-based catalysts at the anode and cathode for widespread development. Research found that the ordered intermetallic compounds served as effective electrocatalysts solve the current dilemma.…”

Alloying Iron into Palladium Nanoparticles for an Efficient Catalyst in Acetylene Dicarbonylation

“…Bimetallic nanocatalysts are a type of heterogeneous catalyst that contains two metal components within a single catalyst and whose composition, size, and configuration can be reasonably controlled. More importantly, it exhibits higher catalytic activity and better selectivity and stability than those of monometallic analogs due to the synergistic effects between the two metallic elements [ 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. In recent decades, several laboratories have focused on the exploitation of non-noble metals and Pd nanoalloy catalysts, such as Pd-Co [ 11 ], Pd-Ni [ 12 ], Pd-Cu [ 13 ], Pd-Mn [ 14 ], and Pd-Fe [ 15 , 16 , 17 ].…”