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Developing efficient electrocatalysts for CO 2 electroreduction to syngas with a specific H 2 /CO ratio over a wide potential window is desperately required but still challenging. In this work, a series of dual-site catalysts composed of iron phthalocyanine (FePc) and ∼18 nm Cobalt nanoparticles (Co NPs) anchored on N-doped carbon matrix has been constructed from zeolitic imidazolate framework-67 (ZIF-67). Benefiting from the synergistic effect of FePc and Co NPs, the derived FePc/Co@N–C catalyst shows impressive capability for CO 2 electrolysis to syngas. By varying the pyrolysis temperatures (600–800 °C) of ZIF-67 and the mass ratio of Co@N–C to FePc (1–3), an adjustable H 2 /CO ratio of 2–4 is obtained, and the value can be maintained stable within a potential window of −0.66 to −0.86 V vs. RHE in an H-type cell. Moreover, this electrocatalyst exhibits favorable stability without distinct performance decay. When conducted in a flow cell, an enhanced catalytic activity is demonstrated with an industrial current density (>100 mA cm−2) at −0.8 V vs. RHE and a steady H 2 /CO ratio of 2 from −0.4 to −0.6 V vs. RHE. This work provides a promising strategy of designing bifunctional electrocatalysts for syngas generation with stable H 2 /CO ratio across a wide potential range. [Display omitted] • Dual-site electrocatalyst composed of FePc and Co NPs is constructed for CO 2 electrolysis to syngas. • High activity, adjustable H 2 /CO ratio (2–4) and favorable stability are demonstrated. • The syngas with specific H 2 /CO ratio can be achieved over a wide potential range. • The synergistic effect of FePc and Co NPs accounts for the impressive performance for CO 2 electrolysis. [ABSTRACT FROM AUTHOR]

Electrochemical CO 2 reduction (ECR) has been considered as the most promising route to convert CO 2 into fuels, but suffers inferior conversion efficiency and product selectivity due to the lack of effective electrocatalysts. Herein, the N-coordinated single-atomic Ni active sites embedded in porous carbon nanotubes (Ni/N-CNTs) are constructed through one-pot pyrolysis strategy as an efficient ECR electrocatalyst. The Zn source in pyrolysis plays a key role in the formation of bamboo-like CNTs, and increased concentrations of surface defects and single-atomic Ni sites of the electrocatalyst. All these benefits endow the electrocatalyst with excellent ECR performance, achieving a large CO Faradaic efficiency (FE CO) up to 98% and turnover frequency up to 304.5 h−1 at a relatively low potential of −0.65 V vs. RHE. Furthermore, over 80% FE CO can be maintained in a wide potential range from −0.57 to −0.81 V. In addition, the electrocatalyst also shows high operation stability for 20 h without obvious FE CO and j CO decay. We believe this study will shed a new light on the design of highly efficient M/N–C catalyst for ECR systems. [Display omitted] • Single-atomic nickel active sites in carbon nanotubes is developed via Zn-assisted pyrolysis method. • High performance for electrochemical CO 2 reduction with CO Faradaic efficiency of 98% at a overpotential of 540 mV. • Improved nanotubular morphology, increased concentrations of defects and single Ni active sites achieved by Zn addition. • Unveiling the decisive catalytic effect of single-atomic Ni sites in catalyzing CO2 electroreduction. [ABSTRACT FROM AUTHOR]

Using aniline as monomer, ammonium persulfate as initiator, ZnCl2 and FeCl3 as metal sources, ZnFe-PANI catalyst precursor was prepared by one-step in-situ chemical polymerization method, and then ZnFe-N-C catalyst was synthesized by high temperature pyrolysis-acidification-secondary pyrolysis. The morphology and structure of the catalyst were characterized by XRD, SEM, Raman and other methods, and its catalytic performance was investigated by the electroreduction reaction of CO2. The results showed that metal doping had little effect on the morphology and structure of N-C materials, but enhanced its structural stability, increased the number of defect sites and active sites, and the area of electrochemical activity, which was conducive to the improvement of reaction performance; When the molar ratio of Zn and Fe was 3 : 1 in the precursor, the obtained sample ZnFe-N-C-3-1 had the best catalytic performance. At an overvoltage of 0.5V, the Faraday efficiency of the CO2 product by electroreduction was as high as 55 %. [ABSTRACT FROM AUTHOR]

Electrocatalytic reduction of CO 2 into syngas (CO and H 2) has been recognized to be a promising approach to achieve carbon neutrality. However, producing syngas with tunable H 2 /CO ratios in a wide range is still challenging. Herein, nitrogen doped graphene aerogel (GA) supported both single-atomic Ni and Ni nanoparticles (NPs) with a surface atomic ratio of 1.11 were constructed by using layered double hydroxide (LDHs) and g-C 3 N 4 as Ni and N precursors, respectively. H 2 and CO are the only products of CO 2 electroreduction and the ratio of H 2 /CO can be tuned from 0.4 to 2.5 by changing applied potentials. In addition, the catalyst exhibits a large CO Faradaic efficiency (74%) and good long-term stability (12 h) at a relatively small potential (−0.67 V vs. RHE). This study will shed a new light on the construction of bifunctional catalysts for efficient tunable syngas generation via electroreduction of CO 2. [Display omitted] • N doped graphene aerogel supported Ni electrocatalysts were constructed. • Both single-atomic Ni and Ni nanoparticles were contained in the electrocatalyst. • High catalytic performance for electrochemical CO 2 reduction to tunable syngas. • The decisive role of Ni nanoparticles and single Ni sites in catalyzing H 2 O and CO 2. [ABSTRACT FROM AUTHOR]

Single-atom transition-metal-anchored nitrogen-doped carbon (M-N-C) materials show great potential in electrochemical reduction of CO 2 to CO. However, the development of catalysts with high exposure density of M-N x active sites remains key challenge. Herein, we report an atomically dispersed and highly exposed Fe coordinated to nitrogen (Fe-N x) active sites doped within carbon nanorods (Fe–N–C) by pyrolysis of sea urchin-like FeOOH-polyaniline (FeOOH-PANI) composite. Results from X-ray photoelectron spectra (XPS) and operando X-ray absorption fine structure (XAFS) spectra confirmed the atomically dispersed Fe species and indicated the Fe coordinated with four N atoms to form the highly exposed Fe-N x active sites. Detailed examination of the Fe–N–C electrocatalyst reveals a high selectivity for CO 2 reduction, presenting CO Faradaic efficiency (FE CO) of 95% with CO partial current density (j CO) of 1.9 mA cm−2 at a relatively low overpotential of 530 mV. The high-performance is a result of the porous structure of catalyst with highly exposed Fe-N x active sites, as well as the larger specific surface area and electrochemical active surface area. Our work proposes an effective and feasible way to designing M-N-C catalysts for efficient electrochemical reduction of CO 2. [ABSTRACT FROM AUTHOR]

Using aniline as monomer, ammonium persulfate as initiator, ZnCl2 and FeCl3 as metal sources, ZnFe-PANI catalyst precursor was prepared by one-step in-situ chemical polymerization method, and then ZnFe-N-C catalyst was synthesized by high temperature pyrolysis-acidification-secondary pyrolysis. The morphology and structure of the catalyst were characterized by XRD, SEM, Raman and other methods, and its catalytic performance was investigated by the electroreduction reaction of CO2. The results showed that metal doping had little effect on the morphology and structure of N-C materials, but enhanced its structural stability, increased the number of defect sites and active sites, and the area of electrochemical activity, which was conducive to the improvement of reaction performance; When the molar ratio of Zn and Fe was 3 : 1 in the precursor, the obtained sample ZnFe-N-C-3-1 had the best catalytic performance. At an overvoltage of 0.5V, the Faraday efficiency of the CO2 product by electroreduction was as high as 55 %. [ABSTRACT FROM AUTHOR]

VO 2 (B) is a promising cathode candidate for aqueous zinc ion batteries owing to its special tunnel lattice structure. However, the zinc storage mechanisms of VO 2 (B) are elusive over large voltage range, especially at the high potential. Via combined structure and composition characterizations such as X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy as well as electrochemical tests, it is demonstrated that VO 2 (B) goes through a conversion reaction when the potential approaching about 1.5 V during the first charging process. The obtained conversion product Zn 3 (OH) 2 V 2 O 7 ·2H 2 O shows high zinc ion storage capacity of 330 mA h g−1 at 0.1 A g−1, fast zinc ion diffusion kinetics, and high rate performances (130 mA h g−1 at 10 A g−1). This work provides a novel strategy for the rational design of electrode materials with large voltage range, especially for aqueous multi-valence ion batteries. Image 1 • A new in-situ electrochemical conversion mechanism of the VO 2 (B) cathode is proposed. • The conversion product Zn 3 (OH) 2 V 2 O 7 ·2H 2 O exhibits the enhanced battery performances. • This work provides a novel strategy to design electrode materials with large voltage range. [ABSTRACT FROM AUTHOR]