Boosting the Electrocatalytic Formic Acid Oxidation Activity via P-PdAuAg Quaternary Alloying

Abstract

Direct formic acid fuel cells (DFAFCs) are considered promising sustainable power sources due to their high energy density, nonflammability, and low fuel crossover. However, serious CO poisoning and activity attenuation of the anodic formic acid oxidation reaction (FAOR) greatly restrict the output and durability of DFAFCs. Inspired by the specific relationship between the composition, type, and property of alloys, in this work, we synthesize a series of hybrid substitutional/interstitial quaternary alloys P-PdAuAg by means of a novel polyphosphide route to address these issues. Due to the simultaneous interstitial P-doping and metal (Au, Ag, Pd) co-reduction, the P-PdAuAg quaternary alloy obtained is only 3 nm in diameter with abundant defects. It not only achieves a new high mass activity of 8.08 A mgPd –1 (6.78 A mgcatalyst –1) but also maintains high stability in the high potential range and harsh reaction conditions. Both the activity and anti-poisoning ability are far exceeding those of the currently reported FAOR catalysts. Detailed density functional theory (DFT) calculations reveal that the superb electrochemical performances originate from the shift of the d-band center of Pd as a result of the synergistic electronic/ligand effects between Pd, Au, Ag, and P. The introduction of interstitial P inhibits the occurrence of an indirect reaction pathway on Pd, while Au and Ag suppress the adsorption of CO and optimize the sequential dehydrogenation steps, leading to boosted reaction kinetics and CO tolerance. This work pioneered a facile way for the synthesis of Pd-based substitutional/interstitial hybrid alloys, providing a promising means of further improving the performance of alloying catalysts.

Metal Phosphide: An Atypical Catalytic Site

“…Pang et al developed the (Fe 0.14 Ni 0.47 Co 0.39 ) 2 P catalyst, which had high activity in electrocatalytic water splitting. Huang et al developed P-PdAuAg nanocomposites, which showed enhanced activity in formic acid oxidation reactions.…”

One-pot synthesis of PdAuAg nanocrystals for efficient electrocatalytic oxidation of ethanol: achieving morphology control by independently adjusting metal-atom concentrations

“…15 Zhao and coworkers prepared the P-PdAuAg quaternary alloy with a diameter of only 3 nm and abundant defects, demonstrating both activity and antipoisoning capabilities far exceeding those of currently reported formic acid oxidation catalysts. 16 Despite the successful demonstration of their superior electrocatalytic performance over monometallic counterparts, most products in these studies were small particles lacking well-defined morphology, which hindered systematic investigation into the relationship between structure (i.e., facets and/or porosity) and properties. Thus, there remains a need for an effective method to control the morphology of multimetallic nano-alloys.…”

Pyridine‐Regulated Lamellar Nickel‐Based Metal–Organic Framework (Ni‐MOF) for Nonenzymatic Electrochemical Glucose Sensor

“…The former deliver high specificity, sensitivity, and wide response range. [ 7 ] However, due to the inherent instability of the enzyme molecule, they are sensitive to changes in environmental conditions (e.g., temperature, humidity, and pH). [ 8 ] In addition, enzymes also have the characteristics of high cost and difficult preservation, which limit the development of enzyme‐based electrochemical Glu sensors.…”