Terrace-Rich Ultrathin PtCu Surface on Earth-Abundant Metal for Oxygen Reduction Reaction

The activity and stability of the platinum electrode toward the oxygen reduction reaction are size-dependent. Although small nanoparticles have high Pt utilization, the undercoordinated Pt sites on their surface are assumed to have too strong oxygen binding strength, thus often leading to compromised activity and surface instability. Herein, we report an extended nanostructured PtCu ultrathin surface to reduce the number of low-coordination sites without sacrificing the electrochemical active surface area (ECSA). The surface shows (111)-oriented characteristics, as proven by electrochemical probe reactions and spectroscopies. The PtCu surface brings over an order of magnitude increase in specific activity relative to commercial Pt/C and nearly 4-fold enhancement in ECSA compared to traditional thin films. Moreover, due to the weak absorption of air impurities (e.g., SO2, NO, CO) on highly coordinated sites, the catalyst displays enhanced contaminant tolerance compared with nanoparticulate Pt/C. This work promises a broad screening of extended nanostructured surface catalysts for electrochemical conversions

Heterostructured Ni/NiO Nanocatalysts for Ozone Decomposition

Water vapor is one of the main factors that deactivate an ozone decomposition catalyst, which limits its applications under practical conditions. In this work, a heterostructured Ni/NiO nanocatalyst is synthesized using a citric sol–gel method, which displays 100% removal efficiency to 1000 ppm ozone at room temperature in a dry flow (space velocity 240 000 mL g–1h–1). Importantly, the removal efficiency is still >98% at a high relative humidity RH of 90% after 8 h of testing, which is twice the efficiency of the pure NiO nanoparticles. The high humidity resistance of the Ni/NiO nanocatalyst can be interpreted as the weak adsorption of water on its surface, as proven by H2O temperature-programmed desorption, X-ray photoelectron spectroscopy, and chemiluminescence (CL). Surface atomic models are also established to present the reaction path of ozone on a catalyst surface under high humidity. In addition, as a proof of concept, a heterostructured Ni/NiO foam monolithic catalyst has been synthesized with nearly 100% decomposition efficiency to 10 ppm ozone at RH 90%. Therefore, these results show the great potency of the Ni/NiO heterogeneous nanocatalyst for ozone removal in harsh environments and can improve the understanding of the ozone decomposition process on a catalyst surface under high humidity

General Synthesis of a Diatomic Catalyst Library via a Macrocyclic Precursor-Mediated Approach

Heterogeneous catalysts containing diatomic sites are often hypothesized to have distinctive reactivity due to synergistic effects, but there are limited approaches that enable the convenient production of diatomic catalysts (DACs) with diverse metal combinations. Here, we present a general synthetic strategy for constructing a DAC library across a wide spectrum of homonuclear (Fe2, Co2, Ni2, Cu2, Mn2, and Pd2) and heteronuclear (Fe–Cu, Fe–Ni, Cu–Mn, and Cu–Co) bimetal centers. This strategy is based on an encapsulation–pyrolysis approach, wherein a porous material-encapsulated macrocyclic complex mediates the structure of DACs by preserving the main body of the molecular framework during pyrolysis. We take the oxygen reduction reaction (ORR) as an example to show that this DAC library can provide great opportunities for electrocatalyst development by unlocking an unconventional reaction pathway. Among all investigated sites, Fe–Cu diatomic sites possess exceptional high durability for ORR because the Fe–Cu pairs can steer elementary steps in the catalytic cycle and suppress the troublesome Fenton-like reactions