查看更多>>摘要：Molecular doping approach can effectively modulate the charge transfer kinetics of polymeric carbon nitride (PCN) photocatalyst. Herein, we show that doping of PCN with a strong electron-withdrawing 2,3-diaminopyr-idine (DAP) induces the formation of donor-π-acceptor (D-π-A) network. As formed D-π-A type network demonstrated a photocatalytic hydrogen production activity of 6.56 mmolg~(-1) h~(-1), which is 4.5-times greater than the pure PCN. The optoelectronic features characterized by spectroscopic techniques indicate rapid separation of photoexcited charge carriers and extended light-harvesting ability of DAP-doped PCN. Further, the theoretical analysis revealed that DAP-doped PCN has near-ideal hydrogen adsorption free energy of - 0.11 eV, which supports the excellent hydrogen production performance. Importantly, the hydrogen production activity demonstrated here outperforms several state-of-art molecular-doped PCN-based catalysts. This study sheds light on the effective production of PCN-based D-π-A networks using conjugated heterocyclic compounds.
查看更多>>摘要：Titanium-substituted cerium-oxo-based UiO MOFs with terephthalate linkers modified by various groups (-Br, -NH2, -NO2) or their derivatives (N-heterocyclic or biphenyl groups) were combined with titanium dioxide in a multistep route to obtain a core-shell-like architecture. DFT simulations showed that Ce- and bimetallic Ti/Ce-MOFs exhibited different charge compensation. Extended characterization revealed the formation of hetero-junctions between the (Ti/Ce)UiO-X MOFs and TiO2 nanoflowers, suitable band edge positions, and high specific surface area and porosity, which resulted in effective electron transfer and excellent photocatalytic activity. The photoactivity of the (Ti/Ce)UiO-X@TiO2 composites for hydrogen production or phenol degradation varied according to the order -NH2 > biphenyl > -N- > -H > -Br > -NO2 > pristine TiO2 or -Br > -NH2 > -NO2 > -N-> -H > biphenyl > pristine TiO2. The photocatalytic hydrogen production rate of (Ti/Ce)UiO-66-NH2@TiO2 was 4724 and 19.3 μmol·g_(cat)~(-1) after 4 h of UV-Vis and visible light irradiation, which were 79 and 19 times higher than that of pristine rutile, respectively.
查看更多>>摘要：Much work in the past four decades has focused on CdS as photocatalyst for water splitting. Recently, Ni3S4 has been reported to be more active than IrO2 as an electrocatalyst for water oxidation. Herein we report a positive role of Ni3S4 in CdS photocatalysis. Reaction was conducted in aqueous suspension under a 420 nm light, either for proton reduction to H2 in presence of Na2S and Na2SO3, or for O2 reduction to H2O2 without addition of any sacrifices. In both cases, M3S4 were nearly not active. After Ni3S4 loading, however, the rates of H2 and H2O2 production on CdS increased by factors as much as 21 and 3, respectively. Furthermore, Ni3S4/CdS was more efficient than CdS for proton and O2 reduction on a cathode, respectively, while Ni3S4/CdS was less efficient than CdS for the photoelectron accumulation on an electrode at open circuit potential. Based on the solid photo-luminescence spectra and band edge potentials, a possible mechanism is proposed, involving the interfacial electron transfer from CdS to Ni3S4, followed by an increased surface reaction, for proton (oxygen) reduction on Ni3S4 sites, and for sulfide (water) oxidation on CdS sites, respectively.
查看更多>>摘要：The sluggish kinetics of oxygen electrode reactions is a bottleneck for the development of rechargeable Zn-air batteries (ZABs). Herein, we report a bifunctional electrocatalyst synthesized by anchoring individually dispersed Ni single atoms on N-doped carbon nanosheets (Ni SAs-NC), which exhibits an outstanding overall performance for oxygen reduction reaction (ORR) and urea oxidation reaction (UOR). Based on that, a conceptual urea-assisted rechargeable ZAB by coupling ORR with UOR of a low thermodynamic potential is demonstrated to have significantly decreased charging voltage and high urea elimination rate. The high bifunctional electrocatalytic activities of Ni SAs-NC endow the urea-assisted ZAB with a dramatically increased energy conversion efficiency of 71.8%, which is improved by 17.1% as compares with the conventional ZABs. The successful implementation of Ni SACs based urea-assisted rechargeable ZABs with an improved energy conversion efficiency may prompt ZAB technology towards practical applications.
查看更多>>摘要：Precise control is critically significant for synthesizing highly efficient bifunctional water splitting electro-catalyst. This study has developed a facile strategy for fabricating porous Ni-Co-Fe ternary metal phosphides nanobricks (denoted as Ni-Co-Fe-P NBs) with specified components and morphology. The optimized sample of Ni-Co-Fe-P NBs showed remarkable electrocatalytic performance in 1.0 M KOH. When served as bifunctional electrocatalyst for overall water splitting, the Ni-Co-Fe-P NBs required a low cell voltage of 1.46 V to achieve a current density of 10 mA cm~(-2) along with superior durability. Density functional theory (DFT) calculation revealed that the homogeneously distributed Ni and Fe can optimize △GH* , and therefore enhance their HER activity. In the case of OER, introducing Ni, Fe and P can promote the formation of desired Co~(4+) sites and stabilize O-containing intermediates (H*, OH*, OOH*) on the surface of the catalysts.
查看更多>>摘要：Hydrogen production via solar and electrochemical water splitting is a promising approach for storing solar energy and achieving a carbon-neutral economy. However, hydrogen production by photoelectric coupling remains a challenge. Here, by the cooperative coupling of heteroatoms and a heterojunction interface engineering strategy in a limited space, a honeycomb porous Co2P/Mo2C@NC catalyst was obtained for the first time. In contrast most traditional chemical syntheses, this method maintains excellent electrical interconnections among the nanoparticles and results in large surface areas and many catalytically active sites. Theoretical calculations reveal that the construction of a heterostructure can effectively lower the hydrogen evolution reaction and oxygen evolution reaction barriers as well as improve the electrical conductivity, consequently enhancing the electrochemical performance. Significantly, the overall water-splitting hydrolytic tank assembled using AsGa solar cells enabled the system to achieve a stable solar hydrogen conversion efficiency of 18.1%, which provides a new approach for facilitating large-scale hydrogen production via portable water hydrolysis driven by solar cells.
查看更多>>摘要：Metal tellurides attract recent attention because of their promising applications as effective catalysts for the oxygen evolution reaction (OER). However, inappropriate adsorption energy between OER intermediates and telluride leads to an unsatisfactory electrocatalytic intrinsic activity. Herein, we adopt a unique in-situ cathodic electrochemical activation process to facilitate the surface self-reconstruction to form oxygen vacancy (OV)-rich TeO2 layer onto Fe-doped NiTe (OV@Fe-NiTe). Characterizations and theoretical calculation demonstrate that the presence of the OV-rich TeO2 layer realizes the adjustment of D-band center of the active site that translates into an enhancement of the adsorption of *OOH intermediate and thus the optimization of the OER pathway. Consequently, the OV@Fe-NiTe only requires an ultralow overpotential of 245 mV to drive 100 mA cm~(-2) in 1 M KOH, 95 mV lower than that of Fe-NiTe, and hence becoming the best water oxidation electrocatalysts amongst recently reported telluride electrocatalysts. This study presents a unique strategy to exploit telluride-based catalysts through electrochemical surface engineering.
查看更多>>摘要：Developing easy-to-make and excellent bifunctional electrocatalysts for water splitting over a wide pH range is a challenging yet appealing topic. Herein, based on integration of vacancy engineering and electronic modulation, a high-performance vs-Ru-Ni9S8 electrocatalyst for water splitting was constructed via a cost-effective one-step hydrothermal method. Under the synergistic regulation of Ru-doping and sulfur vacancies, the vs-Ru-Ni9S8 exhibited the outstanding electrocatalytic performance and long-time durability, along with ultra-low OER overpotentials of 218 and 268 mV at 100 and 300 mA cm~(-2) in alkaline electrolyte and low HER overpotentials of 56, 131, 94 mV at 10 mA cm~(-2) in acidic, neutral, alkaline electrolyte. Impressively, 1.47 and 1.68 V of voltages were needed to achieve 10 and 300 mA cm~(-2) for the vs-Ru-Ni9S8 (+, -) cell. Our DFT results revealed that the doping Ru atom played a crucial role in regulating electron density in OER, rather than served as a catalytic active site. More importantly, we corroborated the active Ni-vacancy pair composed of Ni atom and sulfur vacancy, as an active site, and its catalytic synergy in OER. Especially, a vacancy-metal synergetic mechanism for OER was suggested to correctly describe the OER process and the role of vacancy in catalytic process. Our work provides a simple and effective strategy for fabricating high-performance catalysts and an in-depth understanding of OER.
查看更多>>摘要：Heat/persulfate (PS)-based chemical oxidation for soil and groundwater remediation is limited in its ability to degrade highly chlorinated compounds (HCCs) due to their insensitivities to electrophilic radicals (e.g. SO4~(·-) and ·OH). Herein, we developed a universal system for reductive radicals formation with nucleophilic character through hydrogen atom transfer between low-molecular-weight organic acids (LMWOAs) and electrophilic radicals. Specifically, we found that oxalic acid could regulate heat/PS system to generate carbon dioxide radical anion (CO2~(·-)) which initiated nucleophilic reduction of dichlorodiphenyltrichloroethane (DDT), followed by SO4~(·-)/·OH-initiating electrophilic oxidization of dechlorination intermediates. The CO2~(·-) was oxygen-dependent, resulting in higher DDT degradation performance in anaerobic environment, and corresponding degradation pathways were elucidated by theory calculations. Most importantly, compared to heat/PS system, appropriately distributing the amount of CO2~(·-) and SO~(·-)/·OH by regulating additive concentration of oxalic acid significantly increased degradation efficiency (32.34%), degradation rate (174.20%), and mineralization efficiency (29.57%) on DDT, revealing great potentials of proposed system.
查看更多>>摘要：Hollow nanocatalysts, which are vehemently researched for their delimited cavity and enclosed shell, could manifest tunable focal properties besides well-defined active sites, thus enhancing the catalytic functionality. Herein, nickel-silicate hollow spheres (NHSs) with varied shell thickness and interior cavity size were commensurately designed. Distinction between various NHSs-derived Ni/SiO2 with identically mimicked morphologies was realized by examining their catalytic performance for methane dry reforming (DRM) reaction with sweeping pre- and post-reaction characterizations (TEM, XPS, XANES, in-situ DRIFTS). Besides facilitating the DRM reaction up to its thermodynamic limit, it was revealed that optimal NHS conformation is beneficial as a potential natural barrier against sintering and coking bottlenecks. Furthermore, a fine-tuned shell composition could endow improved Ni-sintering resistivity and enhanced reactivity to the NHS nanocatalysts. Our findings prove that the hollow interior space with a conducive shell thickness positively influences the reactant conversion and coking hindrance during the DRM reaction.
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