Search

Reverse water gas shift (RWGS) reaction is an attractive approach to convert CO2 with renewable H2 to produce CO. However, this reaction is always accompanied by undesirable methanation reaction lowering the CO selectivity, particularly, at low reaction temperature and on Ni catalysts. Herein, a strategy of deposition of inert Ag on the surface of Ni to block methanation reaction during RWGS for selective conversion of CO2 toward CO was reported. Characterizations showed that in contrast to formation of bulk Ni−Ag alloy, both Ag particle and highly dispersed Ag are direct contacting with Ni particle. Surface Ag modifies the property of Ni geometrically and electronically, resulting in reduced accessible surface Ni sites and Ni ensemble size, as well as electron transfer from Ni to Ag. Consequently, both the amount and strength of CO adsorption are reduced, which facilitates CO desorption and reduces CO methanation activity. The Ag modification tunes Ni/SiO2 from selective methanation to selective RWGS, with 100 % CO selectivity on Ni‐0.3 Ag/SiO2 (Ag/Ni=0.3) at 400 °C with gas hourly space velocity (GHSV) >300 L g−1 h−1 and CO selectivity is >80.7 % even at a low GHSV of 15 L g−1 h−1. Moreover, the Ni‐0.3 Ag/SiO2 appears to be very stable for RWGS reaction. [ABSTRACT FROM AUTHOR]

There is no doubt that hydrogen energy can play significant role in promoting the development and progress of modern society. The utilization of hydrogen energy has developed rapidly, but it is far from the requirement of human. Therefore, it is very urgent to develop methodologies and technologies for efficient hydrogen production, especially high activity and durable electrocatalysts. Here a bimetallic oxide cluster on heterostructure of vanadium ruthenium oxides/graphdiyne (VRuOx/GDY) is reported. The unique acetylene‐rich structure of graphdiyne achieves outstanding characteristics of electrocatalyst: i) controlled preparation of catalysts for achieving multiple‐metal clusters; ii) regulation of catalyst composition and morphology for synthesizing high‐performance catalysts; iii) highly active and durable hydrogen evolution reaction (HER) properties. The optimal porous electrocatalyst (VRu0.027Ox/GDY) can deliver 10 mA cm−2 at low overpotentials of 13 and 12 mV together with robust long‐term stability in alkaline and neutral media, respectively, which are much smaller than Pt/C. The results reveal that the synergism of different components can efficiently facilitate the electron/mass transport properties, reduce the energy barrier, and increase the active site number for high catalytic performances. [ABSTRACT FROM AUTHOR]

Catalytic reduction of CO 2 with renewable H 2 to CO via the reverse water gas shift (RWGS) reaction is an attractive approach to recycle CO 2 and control net emission of CO 2 to atmosphere. However, low activity and high CH 4 selectivity at low temperatures limited the practical implementation of the reaction. Herein, Pt-Re/SiO 2 catalysts with varying amount of Re were prepared with co-impregnation and tested for the RWGS reaction. Characterization results indicated that the oxophilic ReO x (0 ≤ x ≤ 3.5) located in close proximity to Pt particle, modified the surface of Pt by both partial coverage and electronic interaction, resulting in the reduced number of sites for and weakened strength of CO adsorption. At 400 °C, the turnover frequency (2.30 s−1) on the optimal Pt-Re/SiO 2 catalyst (Pt/Re = 1.91) is 3.9 times higher than that on Pt/SiO 2 under differential conditions, and the apparent activation energy is lowered. In contrast to Re/SiO 2 which produces significant amount of CH 4 , the CO selectivity on Pt-Re/SiO 2 maintained > 96.2 % under integral conditions. Reaction order analysis revealed that Pt facilitates H 2 activation whereas the oxophilic ReO x enhances CO 2 adsorption and activation. The perimeter sites at the Pt/ReO x interface with a balanced hydrogenation and C-O cleavage properties synergistically improve the RWGS activity while inhibiting CH 4 production. [Display omitted] • ReO x (0 ≤ x ≤ 3.5) modified the surface of Pt by both partial coverage and electronic interaction. • ReO x modification weakened CO adsorption on Pt and enhanced CO selectivity (> 96.2 %). • TOF of RWGS on optimal Pt-Re/SiO 2 (2.30 s−1) is 3.9 times higher than that on Pt/SiO 2. • Reaction kinetic analysis revealed Pt and ReO x activate H 2 and CO 2 , respectively. • The synergy of Pt and ReO x enhanced RWGS activity and inhibited CH 4 formation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The content of pyridinic N in Co-N-C catalysts is modulated via solvent effect. • DFT calculations reveal that the synergy of pyridinic-N and CoN x significantly accelerate the ORR. • The content of pyridine N in the prepared atomically dispersed Co-N-C catalyst is up to 43.7%. • The optimal Co-N-C catalyst exhibits high ORR activity in acid media. Rational design of platinum group metal (PGM)-free catalysts, e.g., M−N−C catalysts, with well-defined structure is highly essential to replace the conventional PGM-based catalysts towards oxygen reduction reaction (ORR), which, however, is still challenging. Particularly, extra nitrogen plays an important role in the ORR performance of M−N−C but the mechanism remains unclear. In this work, a facile modulation strategy based on solvent effect is proposed to tailor nitrogen dopants in the metal organic frameworks (MOFs)-derived Co-N-C catalysts. DFT calculations reveal that the synergy of pyridinic-N and CoN x significantly accelerate the ORR. Reasonably, the optimized Co-N-C catalyst shows superior onset potential (E onset) of 0.915 V and half-wave potential (E 1/2) of 0.785 V toward ORR. This work may pave an avenue for the precise construction of active moieties in large-scale preparation of PGM-free ORR catalyst. [ABSTRACT FROM AUTHOR]