Research

12 pages, 2984 KiB

Open AccessArticle

Cu/CuOx@C Composite as a High-Efficiency Electrocatalyst for Oxygen Reduction Reactions

by Ding Zhang, Yun-Fei Li, Li-Xue Liu, Lei Duan, Zhi-Li Ren, Shou-Dong Xu, Liang Chen, Hui-Juan Guo, Yi Huang, Li-Juan Shi and Qun Yi

Catalysts 2022, 12(12), 1515; https://doi.org/10.3390/catal12121515 - 25 Nov 2022

Cited by 3 | Viewed by 1357

Abstract

Among clean energy transformation devices, fuel cells have gained special attention over the past years; however, advancing appropriate non-valuable metal impetuses to halfway supplant the customary Pt/C impetus is still in progress. In this paper, we propose a specific electrocatalyst in the formula [...] Read more.

Among clean energy transformation devices, fuel cells have gained special attention over the past years; however, advancing appropriate non-valuable metal impetuses to halfway supplant the customary Pt/C impetus is still in progress. In this paper, we propose a specific electrocatalyst in the formula of highly-active Cu species, associated with coated carbon (Cu@C-800), for oxygen reduction reaction (ORR) through post-treatment of a self-assembled precursor. The optimized catalyst Cu@C-800 showed excellent ORR performance (i.e., the onset potential was 1.00 V vs. RHE, and half-wave potential of 0.81 V vs. RHE), high stability, resistance to methanol, and high four-electron selectivity. The enhancement is attributed to the synergy between the carbon matrix and a high explicit surface region and rich Cu nano-species. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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17 pages, 3928 KiB

Open AccessArticle

Interfacial Electronic Rearrangement and Synergistic Catalysis for Alkaline Water Splitting in Carbon-Encapsulated Ni (111)/Ni₃C (113) Heterostructures

by Xiaoyu Li, Zhenbo Peng, Dongmei Jia, Yikang Wang, Wenbo Wu, Ping Deng, Mengqiu Xu, Xudong Xu, Gan Jia, Wei Ye and Peng Gao

Catalysts 2022, 12(11), 1367; https://doi.org/10.3390/catal12111367 - 04 Nov 2022

Cited by 2 | Viewed by 1436

Abstract

The realization of efficient water electrolysis is still blocked by the requirement for a high and stable driving potential above thermodynamic requirements. An Ni-based electrocatalyst, is a promising alternative for noble-metal-free electrocatalysts but tuning its surface electronic structure and exposing more active sites [...] Read more.

The realization of efficient water electrolysis is still blocked by the requirement for a high and stable driving potential above thermodynamic requirements. An Ni-based electrocatalyst, is a promising alternative for noble-metal-free electrocatalysts but tuning its surface electronic structure and exposing more active sites are the critical challenges to improving its intrinsic catalytic activity. Here, we tackle the challenge by tuning surface electronic structures synergistically with interfacial chemistry and crystal facet engineering, successfully designing and synthesizing the carbon-encapsulated Ni (111)/Ni₃C (113) heterojunction electrocatalyst, demonstrating superior hydrogen evolution reaction (HER) activities, good stabilities with a small overpotential of −29 mV at 10 mA/cm², and a low Tafel slope of 59.96 mV/dec in alkaline surroundings, approximating a commercial Pt/C catalyst and outperforming other reported Ni-based catalysts. The heterostructure electrocatalyst operates at 1.55 V and 1.26 V to reach 10 and 1 mA cm⁻² in two-electrode measurements for overall alkaline water splitting, corresponding to 79% and 98% electricity-to-fuel conversion efficiency with respect to the lower heating value of hydrogen. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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12 pages, 3150 KiB

Open AccessArticle

Tailorable Formation of Hierarchical Structure Silica (HMS) and Its Application in Hydrogen Production

by Luming Li, Jie Deng, Zhanglong Guo, Wei Chu and Yan Liu

Catalysts 2022, 12(9), 1061; https://doi.org/10.3390/catal12091061 - 17 Sep 2022

Viewed by 1368

Abstract

Relentless endeavors have been committed to seeking simple structure-directing agents for synthesizing hierarchical mesoporous silica (HMS) materials but remaining challenges. In this contribution, we offered an improved one-pot hydrothermal route to prepare HMS materials using a single non-ionic triblock copolymer (F127) structure-directing agent [...] Read more.

Relentless endeavors have been committed to seeking simple structure-directing agents for synthesizing hierarchical mesoporous silica (HMS) materials but remaining challenges. In this contribution, we offered an improved one-pot hydrothermal route to prepare HMS materials using a single non-ionic triblock copolymer (F127) structure-directing agent under a mild polycarboxylic (citric acid) mediated condition. Via studies of key synthetic parameters including acid concentration, crystallization temperature and aging time, it was found that citric acid medium presents an important bridging effect under the optimal concentration from 0.018 M (pH = 2.57) to 1.82 M (pH = 1.09), contributing to the self-assemblage of partially protonated non-ionic triblock copolymer and tetraethyl orthosilicate (TEOS) into a high-quality multistage structure of silica materials. The specific surface area (SSA) of HMS shows a volcanic trend and is closely associated with the concentration of citric acid while the highest SSA of 739.9 m²/g can be achieved at the citric concentration of 0.28 M. Moreover, the as-synthesized HMS-CTA supported Ni/CeO₂ catalysts indicate an excellent production of hydrogen through dry reforming of methane (DRM) reaction over 172 h stability. The improved, facile synthesis strategy under polycarboxylic medium displays an expanded perspective for synthesizing other mesoporous materials in a wide range of applications such as catalytic material carriers and drug inhibitors. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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19 pages, 3762 KiB

Open AccessArticle

Uniformly Dispersed Cu Nanoparticles over Mesoporous Silica as a Highly Selective and Recyclable Ethanol Dehydrogenation Catalyst

by Yan Hao, Dajie Zhao, Wen Liu, Min Zhang, Yixiao Lou, Zhenzhen Wang, Qinghu Tang and Jinghe Yang

Catalysts 2022, 12(9), 1049; https://doi.org/10.3390/catal12091049 - 15 Sep 2022

Cited by 6 | Viewed by 2403

Abstract

Selective dehydrogenation of ethanol to acetaldehyde has been considered as an important pathway to produce acetaldehyde due to the atom economy and easy separation of acetaldehyde and hydrogen. Copper catalysts have attracted much attention due to the high activity of Cu species in [...] Read more.

Selective dehydrogenation of ethanol to acetaldehyde has been considered as an important pathway to produce acetaldehyde due to the atom economy and easy separation of acetaldehyde and hydrogen. Copper catalysts have attracted much attention due to the high activity of Cu species in O-H and C-H bonds oxidative cleavage, and low process cost; however, the size of the Cu nanoparticle is difficult to control since it is easily suffers from metal sintering at high temperatures. In this work, the Cu/KIT-6 catalyst exhibited an ultra-high metal dispersion of 62.3% prepared by an electrostatic adsorption method, due to the advantages of the confinement effect of mesoporous nanostructures and the protective effect of ammonia water on Cu nanoparticles. The existence of an oxidation atmosphere had a significant effect on the valence state of copper species and enhancing moderate acid sites. The catalyst treated by reduction and then oxidation possessed a moderate/weak acid site ratio of ~0.42 and a suitable proportion of Cu⁺/Cu⁰ ratio of ~0.53, which conceivably rendered its superior ethanol conversion of 96.8% and full acetaldehyde selectivity at 250 °C. The catalyst also maintained a high selectivity of >99% to acetaldehyde upon time-on-stream of 288 h. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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16 pages, 22807 KiB

Open AccessArticle

Embedding Thiophene-Amide into g-C₃N₄ Skeleton with Induction and Delocalization Effects for High Photocatalytic H₂ Evolution

by Shuang Tang, Yang-Sen Xu and Wei-De Zhang

Catalysts 2022, 12(9), 1043; https://doi.org/10.3390/catal12091043 - 14 Sep 2022

Cited by 8 | Viewed by 1903

Abstract

Molecular skeleton modification has become a recognized method that can effectively improve the photocatalytic performance of g-C₃N₄ because it not only effectively promotes charge separation, but also tunes the conjugated system of g-C₃N₄ to make it more [...] Read more.

Molecular skeleton modification has become a recognized method that can effectively improve the photocatalytic performance of g-C₃N₄ because it not only effectively promotes charge separation, but also tunes the conjugated system of g-C₃N₄ to make it more conducive to photocatalytic reaction. Herein, thiophene-amide embedded g-C₃N₄ (TA-CN-x) was successfully prepared by simple one-step thermal polycondensation using urea as a precursor and ethyl-2-amino-4-phenylthiophene-3-carboxylate (EAPC) as an additive. After embedding with thiophene-amide, the induction and delocalization effects are formed in TA-CN-x, which significantly improves the migration efficiency of photogenerated charge carriers. Meanwhile, the conjugate structure is changed due to structural modification, resulting in significant enhancement of visible light absorption compared to the pure g-C₃N₄ (CN). Specifically, the optimized photocatalytic H₂ evolution rate of TA-CN-2 reaches 245.4 μmol·h⁻¹, which is 8.4 times that of CN (with Pt nanoparticles as a co-catalyst), and the apparent quantum efficiency (AQY) at 450 nm is 13.6%. This work opens up a new modification process for fully tapping the photocatalytic hydrogen absorption potential of g-C₃N₄-based materials. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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11 pages, 4000 KiB

Open AccessArticle

Coupling Interface Construction of Ni(OH)₂/MoS₂ Composite Electrode for Efficient Alkaline Oxygen Evolution Reaction

by Ge Liu, Xuezhi Ouyang, Xue-Ling Wei, Wei-Wei Bao, Xiao-Hua Feng and Jun-Jun Zhang

Catalysts 2022, 12(9), 966; https://doi.org/10.3390/catal12090966 - 29 Aug 2022

Cited by 6 | Viewed by 1618

Abstract

The transition metal-based catalysts have excellent electrochemical oxygen evolution reaction catalytic activity in alkaline electrolytes, attracting a significant number of researchers’ attention. Herein, we used two-step hydrothermal and solvothermal methods to prepare a Ni(OH)₂/MoS₂/NF electrocatalyst. The electrocatalyst displayed outstanding [...] Read more.

The transition metal-based catalysts have excellent electrochemical oxygen evolution reaction catalytic activity in alkaline electrolytes, attracting a significant number of researchers’ attention. Herein, we used two-step hydrothermal and solvothermal methods to prepare a Ni(OH)₂/MoS₂/NF electrocatalyst. The electrocatalyst displayed outstanding OER activity in 1.0 M KOH electrolyte with lower overpotential (296 mV at 50 mA·cm⁻²) and remarkable durability. Comprehensive analysis shows that reinforcement of the catalytic function is due to the synergistic effect between Ni(OH)₂ and MoS₂, which can provide more highly active sites for the catalyst. This also provides a reliable strategy for the application of heterogeneous interface engineering in energy catalysis. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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11 pages, 1837 KiB

Open AccessFeature PaperArticle

Effects of Artificial River Water on PEM Water Electrolysis Performance

by Ryoya Yoshimura, SoeHtet Wai, Yasuyuki Ota, Kensuke Nishioka and Yoshihiro Suzuki

Catalysts 2022, 12(9), 934; https://doi.org/10.3390/catal12090934 - 24 Aug 2022

Cited by 6 | Viewed by 3616

Abstract

Hydrogen, a clean and renewable energy source, is a promising substitute for fossil fuels. Electricity-driven water electrolysis is an attractive pathway for clean hydrogen production. Accordingly, the development of electrolysis cells has drawn researchers’ attention to capital costs related to noble catalyst reduction [...] Read more.

Hydrogen, a clean and renewable energy source, is a promising substitute for fossil fuels. Electricity-driven water electrolysis is an attractive pathway for clean hydrogen production. Accordingly, the development of electrolysis cells has drawn researchers’ attention to capital costs related to noble catalyst reduction and membrane degradation by the contaminations. In the literature, polymer electrolyte membranes (PEMs) have been studied on single cations contamination. In this study, we investigated the performance of a PEM on monovalent and divalent cation contamination by feed water. Artificial river water, called soft water, was used to analyze the effect of impurities on the PEM. The results demonstrated that the operating voltage drastically increased and induced cell failure with increasing Mg²⁺ and Ca²⁺ concentrations; however, it did not increase for Na⁺ and K⁺ after increase in voltage. Therefore, divalent cations have a stronger affinity than monovalent cations to degrade PEM and should be effectively excluded from the feed water. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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13 pages, 3709 KiB

Open AccessArticle

Vanadium Nitride Supported on N-Doped Carbon as High-Performance ORR Catalysts for Zn–Air Batteries

by Yidan Fu, Lina Han, Pengfei Zheng, Xianhui Peng, Xianglan Xian, Jinglin Liu, Xiaoyuan Zeng, Peng Dong, Jie Xiao and Yingjie Zhang

Catalysts 2022, 12(8), 877; https://doi.org/10.3390/catal12080877 - 09 Aug 2022

Cited by 7 | Viewed by 1787

Abstract

It is desirable to prepare low-cost non-noble metal catalysts using a simple and efficient method. Herein, we display for the first time that nitrogen-doped hierarchical porous carbon-supported vanadium nitride (VN/NC/C-x) catalysts can be regulated by dicyandiamide (DCDA). The introduction of DCDA not only [...] Read more.

It is desirable to prepare low-cost non-noble metal catalysts using a simple and efficient method. Herein, we display for the first time that nitrogen-doped hierarchical porous carbon-supported vanadium nitride (VN/NC/C-x) catalysts can be regulated by dicyandiamide (DCDA). The introduction of DCDA not only effectively controls the pore structure, but also plays an important role in adjusting oxygen vacancies and d-electrons. In addition, DCDA is not only a significant raw material for the N-doped carbon, but also a nitrogen source for the preparation of vanadium nitride. The VN/NC/C-3 catalyst was prepared after optimization of the preparation parameters, and the macro/micro structure demonstrates a superior ORR performance in alkaline media with a positive onset potential of 0.85 V and a half-wave potential of 0.75 V, the limiting current density is as high as 4.52 mA·cm⁻², and the Tafel slope is only 75.54 mV·dec⁻¹. The VN/NC/C-3-based Zn–air battery exhibits a highest peak power density (161.82 mW∙cm⁻²) and an excellent energy density (702.28 mAh·kg_Zn⁻¹ and 861.51 Wh·kg_Zn⁻¹). This work provides a valuable synthetic approach for the preparation of other transition metal nitride catalysts with a relative economic value and high performance. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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9 pages, 1916 KiB

Open AccessFeature PaperArticle

Photocatalytic CO₂ Reduction Coupled with Alcohol Oxidation over Porous Carbon Nitride

by Chuntian Qiu, Shan Wang, Jiandong Zuo and Bing Zhang

Catalysts 2022, 12(6), 672; https://doi.org/10.3390/catal12060672 - 20 Jun 2022

Cited by 15 | Viewed by 2178

Abstract

The photocatalytic transformation of CO₂ to valuable man-made feedstocks is a promising method for balancing the carbon cycle; however, it is often hampered by the consumption of extra hole scavengers. Here, a synergistic redox system using photogenerated electron-hole pairs was constructed by [...] Read more.

The photocatalytic transformation of CO₂ to valuable man-made feedstocks is a promising method for balancing the carbon cycle; however, it is often hampered by the consumption of extra hole scavengers. Here, a synergistic redox system using photogenerated electron-hole pairs was constructed by employing a porous carbon nitride with many cyanide groups as a metal-free photocatalyst. Selective CO₂ reduction to CO using photogenerated electrons was achieved under mild conditions; simultaneously, various alcohols were effectively oxidized to value-added aldehydes using holes. The results showed that thermal calcination process using ammonium sulfate as porogen contributes to the construction of a porous structure. As-obtained cyanide groups can facilitate charge carrier separation and promote moderate CO₂ adsorption. Electron-donating groups in alcohols could enhance the activity via a faster hydrogen-donating process. This concerted photocatalytic system that synergistically utilizes electron-hole pairs upon light excitation contributes to the construction of cost-effective and multifunctional photocatalytic systems for selective CO₂ reduction and artificial photosynthesis. Full article

(This article belongs to the Special Issue Advanced Catalysts for Achieving Hydrogen Economy from Liquids)

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