Regeneration and Enhanced Catalytic Activity of Pt/C Electrocatalysts

By adding pure carbon support to improve the redispersion of platinum (Pt), a sintered Pt/C electrocatalyst for methanol electrooxidation was effectively regenerated in activity and doubled in amount on the basis of a one-step liquid oxychlorination. The apparent activity (mA mg_cata.^–1) of the optimal Pt/C regenerated (Pt 3.3 wt %) is close to the initial fresh Pt/C (Pt 10 wt %) and about two times that of fresh Pt/C (Pt 3.3 wt %), making Pt utilization doubled and then the resource-limited Pt potentially sustainable. The new nucleation of metal atoms on added pure support surface was found to be the key for both the improved redispersion of metal nanoparticles and the effective regeneration of catalytic activity in situ

Highly Efficient Regeneration of Deactivated Au/C Catalyst for 4‑Nitrophenol Reduction

In the present work, we proposed an effective method to regenerate sintered gold catalyst by improving the dispersion of gold nanoparticles. With the liquid oxychlorination reaction, a sintered carbon-supported gold (Au/C) nanocatalyst was effectively regenerated by improving the redispersion of Au nanoparticles with additional carbon support. The Au-catalyzed model reaction between 4-nitrophenol and sodium borohydride (NaBH₄) indicates that the apparent activity of the optimal Au/C regenerated (Au 0.45 wt %) exceeds that of the initial fresh Au/C (Au 1 wt %), making Au utilization tripled and potentially sustainable for their extensive application in industry

Theoretical Study of Resorufin Reduction Mechanism by NaBH₄

In the current work, the whole reduction mechanism of resorufin by sodium borohydride (NaBH₄) has been investigated completely using quantum chemical theory for the first time. The possible pathways for each step were considered as much as possible. The calculated results reveal that the reduction mechanism for resorufin undergoes a nucleophilic addition with BH₄^–, a synchronous proton abstraction from a carbon (C) atom, a protonation in a nitrogen (N) atom, and then a final hydrolysis process to obtain final reduced product dihydroresorufin. Interestingly, it was found that the protonation of N atom could induce a reduced product molecule with a Λ-type structure rather than a planar one, and the large alteration in geometry will induce different optical properties, such as fluorescent or nonfluorescent. More importantly, countercation Na⁺ and solvation effect of H₂O play important roles in reducing the activation energy in elementary steps, and their stabilization effect has been confirmed by NBO analysis. The detailed theoretical investigation for the reduction reaction of resorufin by NaBH₄ will support some guidance for the similar reduction reaction for organic compounds like aldehydes and ketones

Growth Mechanism Deconvolution of Self-Limiting Supraparticles Based on Microfluidic System

The synthesis of colloidal supraparticles (SPs) based on self-assembly of nanoscopic objects has attracted much attention in recent years. Here, we demonstrate the formation of self-limiting monodisperse gold SPs with core–shell morphology based on the building blocks of flexible nanoarms in one step. A flow-based microfluidic chip is utilized to slow down the assembly process of the intermediates, which surprisingly allows for observation of ultrathin gold nanoplates as first intermediates. Notably, these intermediate cannot be observed in traditional synthesis due to their rapid rolling-up to form the second-order nanostructure of flexible hollow nanoarms. The growth mechanism of SPs can then be deconvoluted into two seed-mediated steps. Monte Carlo simulations confirm that the self-limiting growth of binary SPs is governed by a balance between electrostatic repulsion and van der Waals attraction

Morphology-Tuning-Induced Highly Efficient Regeneration of Pt/C Nanoelectrocatalysts

The sintering-induced irreversible deactivation of precious metal nanocatalysts is one of the main obstacles for their sustainable application. Here, by adding fluorine (F)-doped carbon support to improve the redispersion and tune the morphology of platinum (Pt) nanoparticles, a sintered Pt/C electrocatalyst for methanol electro-oxidation was completely regenerated in activity and doubled in amount of catalyst and tripled in metal utilization. The morphology-tuning-induced highly efficient regeneration based on F-doped carbon was further confirmed from the regeneration of a spent Pt/C for fuel cells. The quantum chemical calculation shows that the improved redispersion and the morphology transformation of Pt nanocatalyst could be mainly attributed to the strong interaction between <i>d</i> states of Pt and <i>p</i> states of F doped on carbon. The work presented here indicates that the morphology tuning of metal nanocatalysts is another way for highly efficient regeneration of precious metal nanocatalysts. It also opens a new pathway for people to get new functional materials with tunable morphology sustainably

Pt_0.61Ni/C for High-Efficiency Cathode of Fuel Cells with Superhigh Platinum Utilization

Exploring advanced electrocatalysts to accelerate the sluggish oxygen reduction reaction (ORR) in polymer electrolyte membrane fuel cells (PEMFCs) is a promising route to alleviate the current challenges of fossil fuel exhaustion and environment pollution. Herein, a carbon-supported highly dispersed PtNi nanocatalyst (Pt_0.61Ni/C) with low platinum content of 2.76 wt % was prepared simply based on galvanic replacement for a high-efficiency ORR process. It presents a mass activity of ∼5 times of the conventional Pt-based catalyst at 0.9 V (vs reversible hydrogen electrode (RHE)) and a remarkable durability and methanol tolerance. The acidic fuel cell with such cathode catalyst (Pt_0.61Ni/C) presents a striking performance with maximum power density up to 1.1 W cm^–2 at 80 °C. Due to the extremely low platinum loading in the whole fuel cell, its Pt utilization (0.093 g_Pt kW^–1) is the highest reported ever in H₂/O₂ fuel cells. Such impressive performance of Pt_0.61Ni/C makes the obtained Pt_0.61Ni/C catalyst a very promising alternative to conventional Pt-based catalysts for their large-scale application in future