PtCo@NCs with Short Heteroatom Active Site Distance for Enhanced Catalytic Properties

Abstract

The crucial issue for fuel cells is to improve the activity and durability of Pt-based catalysts. Herein, based on the short distance enhancement effects, a novel PtCo@NC catalyst with remarkably enhanced electrocatalytic properties for methanol oxidation reaction (MOR) in acidic electrolytes is developed by shortening the Pt-Co active site distance. In brief, a series of PtCo@NC catalysts with different Pt-Co biatomic arrangement are precisely synthesized by an in situ reduction-fusion method, achieving Pt-Co structural evolution from a Pt/Co individual monometallic islet (A-700 °C) to PtCo heterodimer (A-800 °C) and then a PtCo alloy (A-900 °C) embedded on nitrogen-doped carbon matrixes. Compared with the Pt/Co monometallic islet and heterodimer, the PtCo@NC (A-900 °C) with the shortest Pt-Co active site distance exhibits the highest mass activity of 2.30 A mg Pt −1 , which is 12.23 times higher than that of commercial Pt/C and exceeds almost all the reported MOR catalysts in acidic electrolytes. Both experiments and density functional theory calculations reveal that the remarkably improved activity stems from the modification of electron distribution around Pt/Co metal centers, thus promoting the rate-determining methanol dehydrogenation step and CO oxidative removal processes, which are dependent on the distance between bimetallic active sites.

Tailored Catalytic Nanoframes from Metal–Organic Frameworks by Anisotropic Surface Modification and Etching for the Hydrogen Evolution Reaction

“…[40] Besides,l ittle oxides and hydroxides of Co (that is,C oO, Co 3 O 4 ,orCo(OH) 2 )isdetected on the surface of the catalysts, may resulting from cyanuric acid chelated on surface.X PS investigation of the Pt 4f spectrum (Figure 4h)r evealed the presence of metallic Pt, whereby two intense peaks were located at 71.8 and 75.2 eV,c orresponding to Pt 0 4f 7/2 and Pt 0 4f 5/2 ,respectively. [36,41] In the case of RuCo/C (Supporting Information, Figure S24), similar results were obtained to those for PtCo/C,a nd ruthenium existed mainly in the metallic Ru form. [34,42] These results again indicated that the etching processes of H 2 PtCl 6 and RuCl 3 were similar.…”

“…01‐1278). This phase transition of Co may originate from alloying with Pt and Ru, which again indicates that the introduced Pt and Ru were dissolved in the metallic Co to form alloys [36, 37] . Furthermore, the XRD results (Supporting Information, Figure S22c) of PdCo/C indicate the presence of Co 3 O 4 (JCPDS No.…”

“…More specifically, the porous and open frame structure can expose a large number of active sites and speed up both electron and mass transfer between the catalyst and the electrolyte, thereby drastically boosting the electrochemical surface area. In addition, an optimal component of noble‐metal doping cobalt alloy could enhance synergistic effects, and reduce the H* absorption free energy, thereby significantly improving the electrocatalytic activity [36, 41] …”

“…This phase transition of Co may originate from alloying with Pt and Ru, which again indicates that the introduced Pt and Ru were dissolved in the metallic Co to form alloys. [36,37] Furthermore,t he XRD results (Supporting Information, Figure S22c Figure 4g,h and the Supporting Information, Figure S23) show peaks corresponding to Co,P t, C, and O. TheC o2p spectrum of PtCo/C (Figure 4g)c an be deconvoluted into eight individual peaks assigned to Co 0 ,C oO x and the corresponding satellites,respectively. [38,39] Thus,the Co 0 binding energies (including 2p 1/2 and 2p 3/2 )o ft he catalyst shift to…”

Multi‐Site Electrocatalysts Boost pH‐Universal Nitrogen Reduction by High‐Entropy Alloys

“…Clearly, different metals may serve different roles and work in a synergetic way to bring excellent NRR performance. Moreover, HEA can shorten the distance between active sites [ 51 ] and provide a huge space for component optimization, advanced knowledge for such a synergetic role between metals can greatly help the rational design of catalysts.…”