Search

Solvent environment engineering is developed to synthesize ZIF-derived hierarchically porous cubic Fe N C(C) catalysts with densely Fe-N x sites. [Display omitted] • The Fe-N x site density of ZIF-derived Fe N C is controlled by changing the solvent. • The Fe N C(C) synthesized in water has a high single Fe atom loading (0.6 at%). • The catalyst displays satisfactory ORR activity under alkaline/acidic environment. • The catalyst presents nice performance in liquid and solid-state Zn-air batteries. Zeolitic imidazole framework (ZIF)-derived iron–nitrogen-carbon (Fe N C) materials are expected to be high-efficiency catalysts for oxygen reduction reaction (ORR). However, increasing the density of active sites while avoiding metal accumulation still faces significant challenges. Herein, solvent environment engineering is used to synthesize the Fe N C containing dense Fe-N x moieties by adjusting the solvent during the ZIF precursor synthesis process. Compared with methanol and water/methanol, the aqueous media can provide a more moderate Fe content for the ZIF precursor, which facilitates the construction of high-density Fe-N x sites and prevent the appearance of iron-based nanoparticles during pyrolysis. Therefore, the Fe N C(C) nanocubes synthesized in an aqueous media have the highest single atom Fe loading (0.6 at%) among the prepared samples, which presents excellent oxygen reduction properties and durability under alkaline and acidic conditions. The advantage of Fe N C(C) is proven in Zn-air batteries, with outstanding performance and long-term stability. [ABSTRACT FROM AUTHOR]

[Display omitted] Enhancing the electrocatalytic oxygen evolution reaction (OER) performance is essential to realize practical energy-saving water electrolysis and CO 2 electroreduction. Herein, we report a bimetallic co-doping engineering to design and fabricate nickel–cobalt-iron collaborative oxy-hydroxide on nickel foam that labeled as NiCoFeO x H y -NF. As expected, NiCoFeO x H y -NF exhibits an outstanding OER activity with current density of 10 mA cm−2 at 194 mV, Tafel slope of 53 mV dec−1, along with the robust long-term stability, which is significantly better than bimetallic NiCo and NiFe combinations. Comprehensive computational simulations and characterizations jointly unveil that the twisted ligand environment induced by heteroatoms ensures the balance strength between the metal–oxygen hybrid orbital states and the oxidized intermediates adsorption, thus lowering the oxygen cycling energy barriers for overcoming the sluggish OER kinetics. Moreover, a novel phase transition behavior is monitored by in-situ Raman spectra under OER operating conditions, which facilitates electron-mass transfer as well as boosts the exposure of activity sites. For practical applications, Ni 2 P-NF || NiCoFeO x H y -NF and Cu || NiCoFeO x H y -NF couples were constructed to realize high-efficiency water electrolysis and CO 2 electrochemical reduction for the production of valuable H 2 and C 2 H 4 , respectively. This work elucidates a novel mechanism by which bimetallic co-doping improves the electrocatalytic OER activity of nickel-based hydroxides. [ABSTRACT FROM AUTHOR]

[Display omitted] Copper-based tandem catalysts are effective candidates for yielding multi-carbon (C2+) products in electrochemical reduction of carbon dioxide (CO 2 RR). However, these catalysts still face a significant challenge regarding in the low selectivity for the production of a specific product. In this study, we report a high selectivity of 77.8 %±2 % at −1.0 V (vs RHE) for the production of C 2 H 4 by using a Cu 88 Ag 12 NW catalyst which is primarily prepared through a combined Cu-Ag co-deposition and wet chemical method, employing an attractive strategy focused on regulating the microenvironment over Cu-Ag nanowires. The experimental and computational studies show that the higher *CO coverage and lower intermediate adsorption energy are important reasons for achieving the high C 2 H 4 selectivity of Cu 88 Ag 12 NW catalyst. Comsol simulation results indicate that dense nanowires exhibit a nano-limiting effect on OH− ions, thereby leading to an increase in local pH and promoting coupling reactions. The catalyst demonstrates no noticeable decrease in current density or selectivity even after 12 h of continuous operation. The Cu-Ag nanowire composite exhibits remarkable catalytic activity, superior faradaic efficiency, excellent stability, and easy synthesis, which highlights its significant potential for electro-reducing carbon dioxide into valuable products. [ABSTRACT FROM AUTHOR]

Coordination environment engineering is developed to synthesize Fe SA /NSC catalysts with the tailored N, S co-coordinated Fe atomic site. [Display omitted] • The Fe-N 3 S active site with the optimized electronic structure is constructed. • S doping promotes the OH* desorption, thus leading to enhanced kinetics process. • The catalyst displays impressive ORR activity in both alkaline and acidic mediums. • The catalyst exhibits excellent performance in Zn-air batteries and fuel cells. Atomically dispersed iron–nitrogen-carbon (FesbndNsbndC) materials have been considered ideal catalysts for the oxygen reduction. Unfortunately, designing and adjusting the electronic structure of single-atom Fe sites to boost the kinetics and activity still faces grand challenges. In this work, the coordination environment engineering is developed to synthesize the Fe SA /NSC catalyst with the tailored N, S co-coordinated Fe atomic site (Fe-N 3 S site). The structural characterizations and theoretical calculations demonstrate that the incorporation of sulfur can optimize the charge distribution of Fe atoms to weaken the adsorption of OH* and facilitate the desorption of OH*, thus leading to enhanced kinetics process and intrinsic activity. As a result, the S-modified Fe SA /NSC exhibits outstanding catalytic activity with the half-wave potentials (E 1/2) of 0.915 V and 0.797 V, as well as good stability, in alkaline and acidic electrolytes, respectively. Impressively, the excellent performance of Fe SA /NSC is further confirmed in Zn-air batteries (ZABs) and fuel cells, with high peak power densities (146 mW cm−2 and 0.259 W cm−2). [ABSTRACT FROM AUTHOR]

[Display omitted] • A Zn 5 (OH) 6 (CO 3) 2 -assisted pyrolysis strategy is proposed to prepare a coupled catalyst. • Fe nanoparticles can optimize electronic structures and d-band center of Fe center. • Fe-FeN-C exhibits eminent ORR activity with a E 1/2 of 0.921 V in alkaline media. • The Zn-air batteries deliver high power density and long-cycle life for 408 h. Fe single-atom catalysts still suffer from unsatisfactory intrinsic activity and durability for oxygen reduction reaction (ORR). Herein, the coexisting Fe single atoms and nanoparticles on hierarchically porous carbon (denoted as Fe-FeN-C) are prepared via a Zn 5 (OH) 6 (CO 3) 2 -assisted pyrolysis strategy. Theoretical calculation reveals that the Fe nanoparticles can optimize the electronic structures and d-band center of Fe active center, hence reducing the reaction energy barrier for enhancing intrinsic activity. The Zn 5 (OH) 6 (CO 3) 2 self-sacrificial template not only can promote the formation of Fe single atoms, but also contributes to the construction of microporous/mesoporous/macroporous structures. Therefore, the obtained Fe-FeN-C exhibits impressive ORR activity with a half-wave potential of 0.921 V, which far exceeds Pt/C. With Fe-FeN-C as the cathode catalyst, the assembled Zn-air batteries delivered a maximum power density of 206 mW cm−2 and a long-cycle life over 400 h. [ABSTRACT FROM AUTHOR]