efficient and earth-abundant catalysts have been successfully developed including nitrogen-doped carbon materials that possess promising electrocatalytic performance for ORR and OER. [6][7][8][9][10] However, it remains challenging for nitrogen-doped carbon materials to achieve competitive performance to precious metal catalysts due to low nitrogen concentration.Graphitic carbon nitrides (g-C 3 N 4 ) have shown promising performance to replace nitrogen-doped carbon as a highly efficient catalyst, owing to its ultrahigh nitrogen content (theoretically estimated to be ≈60%) and easily tailored structure. [11][12][13][14][15] It is also well-known that the electrocatalytic performance is determined by catalyst structure and accessibility of active sites. It is of significant importance to maximize the electrochemical surface area to better facilitate the transport of reactants (OH − and O 2 ), and therefore enhance catalytic activity. [16][17][18] For this aim, various methods have been reported in preparation of porous g-C 3 N 4 . Conventionally, rigid templates (SiO 2 , Al 2 O 3 , and ZnO) are used to fabricate porous g-C 3 N 4 , [19,20] which can effectively improve accessibility and catalytic activity of g-C 3 N 4 . However, these rigid template-based synthesis methods are complicated, involving several steps such as template formation, template dispersion, template removal, and catalyst purification. These time-consuming processes increase the fabrication cost and can even damage the g-C 3 N 4 active sites during template removal by the use of strong acidic or basic etching. Addressing these challenges will require facile and strategic developments to synthesize porous g-C 3 N 4 without using templates.Herein, we developed a top-down and template-free strategy for the fabrication of porous g-C 3 N 4 (PCN) by controlled pyrolysis of Co 2+ /melamine networks in O 2 atmosphere. After mixing PCN with graphene oxide (GO) and thermal treating in sulfur atmosphere, CoS x @PCN/rGO catalyst was synthesized. The developed CoS x @PCN/rGO catalyst exhibited outstanding electrocatalytic activity and stability toward both OER and ORR. The CoS x @PCN/rGO also showed long cyclability as an air electrode in a zinc-air battery system, outperforming Pt and other precious metal electrocatalysts. The remarkable electrocatalytic performance of CoS x @PCN/rGO is attributed to the internally accessible nitrogen sites and the facilitated transport of intermediates in the porous structure.A typical synthesis route of PCN is schematically depicted in Figure 1a: First, cobalt(II) nitrate hexahydrate was mixed with Porous carbon nitride (PCN) composites are fabricated using a top-down strategy, followed by additions of graphene and CoS x nanoparticles. This subsequently enhances conductivity and catalytic activity of PCN (abbreviated as CoS x @PCN/rGO) and is achieved by one-step sulfuration of PCN/ graphene oxides (GO) composite materials. As a result, the as-prepared CoS x @PCN/rGO catalysts display excellent activity and stability towa...

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A series of nickel sulfide nanocrystallines with hierarchical structures was successfully fabricated in situ on a nickel substrate. The nanocrystalline materials with three dimensional (3D) structures were synthesized via self-assembly under moderate conditions, with ethylenediamine and ethylene glycol as the mixed solvents. The structure and morphology of each nickel sulfide could be controlled by adjusting the polarity of the mixed solvents. With the reduced solvent polarity, the 3D flower-like nickel sulfide spheres were transformed into two-dimensional (2D) nanoflakes, then into one-dimensional (1D) prism-like microrods, and finally into 1D pearl-like nanochains. When the nickel sulfides were used as electrode materials in lithium-ion batteries, the obtained samples with different morphologies had different initial discharge capacities. The initial discharge capacity of the as-prepared nickel sulfides with 1D nanostructures reached approximately 550 mA h g(-1), which was higher than that of the samples with 2D and 3D structures. This study explores a novel method to control the synthesis of metal chalcogenides with specific morphologies.

Alkaline-surfactant-polymer (ASP) flooding have been studied and applied in Daqing oil field for more than 15 years, where eight ASP pilot tests of different scales had been conducted and five ASP foods have been pilot tested. Incremental recoveries are from 19.4 to 25%(OOIP).Since the adsorption of each chemical component would have significant impact on the cost-effective and recovery efficiency of the ASP flooding process, laboratory experiments were conducted to investigate the adsorption of each component in reservoir rocks as well as the analysis of the mineral contents and the clay compositions in the reservoir rock taking from the ASP test area in the Daqing Oilfield. In the adsorption study, four chemicals;a surfactant, an alkaline agent, polymers, and a sacrificial agent were used. The results showed that the adsorption of surfactant does not obey the Langmuir adsorption isotherm and has a maximum value of 0.6 mg/m2, but adsorptions of alkali and polymer chemicals do obey the Langmuir adsorption isotherm. Adsorption tests also indicated that the adsorption of surfactant could be reduced by 30% with the addition of 0.15wt% of a bio-surfactant as a sacrificial agent into the key surfactant, ORS-41, solution. In addition to adsorption tests, retention (dynamic adsorption) tests were conducted using reservoir core plugs. The results showed that the sequences and peaks of relative concentration (C/C0) of chemicals in effluent are polymer, alkali, and then surfactant. The results also showed that the adsorption of the surfactant is the greatest among all chemicals. This phenomenon indicates the chromatographic separation of three chemicals transport process in cores. The chemical analysis and the chromatographic separation of these chemicals in produced fluids the previous three pilot tests showed consistent results with laboratory studies, and the degree of retention of the surfactant is proportional to the clay content in field tests. Based on these findings, an ASP flooding pilot test was conducted in the Daqing Oilfield in 1994 with the combination of a bio-surfactant and the key surfactant, ORS-41. Since the adsorption of the bio-surfactant is stronger than ORS-41, the bio-surfactant was used in the ASP pilot test to lower the amount of the more expensive ORS-41. However, the effect of bio-surfactant as sacrificial agent on chromatographic separation of chemicals in ASP flooding (or surfactant lag) is not obvious. Introduction One of the main problems of chemical floods is the adsorption loss of various chemicals in the reservoir. The amount of chemical adsorbed and entrapped in the reservoir has a direct influence on the oil displacement efficiency. The adsorption of single component such as surfactant, alkaline, or polymer on reservoir rocks has been reported in the literature1–3. However, the adsorption of each component in the multi-component ASP system on reservoir rocks in the laboratory and ASP flooding pilot tests have been rarely reported. From the point of view of analytical chemistry, the reservoir can be regarded as a large chromatographic column. In the chemical floods process, the surface of the reservoir rock can selectively adsorb different chemicals because of different molecular sizes and hydrophilic-hydrophobic properties. Because the distribution of the pore size of the porous medium is limited, molecules with high molecular weights and large sizes cannot flow through small pores, therefore, they have less chance to be entrapped in the porous media than the smaller molecules. Since the alkylbenzene sulfonates used in the surfactant flooding is a mixture of sulfonates with different molecular weight, it is evident that the chromatographic separation would occur in the reservoir due to the selective adsorption4–6. Due to the different chemical nature of the chemicals, the retention of the different species must obviously be somewhat different. Chromatographic separation of different type chemicals such as between surfactants, alkaline agents and polymers would also occur in the complex ASP system, but we know nothing about seepage speeds and rentention of each chemical in ASP flooding in reservoir. Because the synergistic effects among the three chemicals in the ASP flooding are important to maximize the incremental oil recovery, the chromatographic separation of chemicals in the displacement process needs to be minimized. If the adsorption of the surfactants or the alkaline was too high, the effectiveness of the ASP system would be reduced due to the increase in the IFT between the ASP slug and crude oil, and therefore, the oil displacement efficiency would be decreased.

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Zn-based catalyst is promising for electrochemical CO2 reduction (CO2RR) because of the abundant reserves and good activity. However, a major challenge still remains in simultaneously achieving both large current density and high Faradaic efficiency. Herein, we report a three-dimensional porous Zn catalyst (HP-Zn) for CO2RR via a simple hydrogen-mediated method, where hydrogen gas bubbles have been utilized as soft templates to generate a series of hierarchical pores in the sample. Benefiting from the high specific surface area (97.2 m2 g–1) and rich mesoporous structure, the as-prepared HP-Zn catalyst displays excellent catalytic activity with a maximum CO Faradaic efficiency of 91.3%, corresponding to a current density of −10.0 mA cm–2, as well as long-term stability, demonstrating a promising potential for the practical application of CO2RR.

In response to the shortage of fossil fuels, efficient electrochemical energy conversion devices are attracting increasing attentions while a daunting challenge regarding the limited electrochemical performance and high cost of...