Facile in-situ deposition of three-dimensional Pt nanoballs of nickel nanorods heterojunction electrodes for hydrogen evolution reaction

Hydrogen is a kind of renewable energy for a friendly environment and can promote carbon emission reduction. The Platinum catalytic electrode is widely applied in hydrogen evolution reaction (HER) of water due to its low overpotential. However, it has affected its commercial application because of its high cost. Therefore, developing heterojunction catalysts with Platinum for HER is an effective way to achieve large-scale hydrogen production. In this work, we present a novel PtNBs/NiNRs heterojunction catalyst via the Pt nanoballs in-situ deposition on Ni nanorods array. The results demonstrate that the PtNBs/NiNRs electrodes have superior catalytic activity for HER in an alkaline condition. The hydrogen overpotential of PtNBs/NiNRs is −61.6 mV (RHE) in the alkaline solution, which is lower than the Pt electrode of −184mV. The Tafel plots and EIS were employed to investigate the mechanism and kinetics of the PtNBs/NiNRs in the alkaline solution. The nanostructures of Ni nanorobs and the Pt nanoballs active sites decrease the charge transfer resistance and increase the charge capacitance for the HER process compared to the Pt electrode. The PtNBs/NiNRs heterojunction catalyst electrodes demonstrate promising applications in HER because of their facile preparation, high efficiency, and low value.     

First row transition metal doped B12P12 and Al12P12 nanocages as excellent single atom catalysts for the hydrogen evolution reaction

The hydrogen evolution reaction (HER) is a promising process to produce high purity hydrogen gas. However, the overpotential of this reaction hinders its practical applications. Single atom catalysts (SACs) are recently investigated by the scientific community to facilitate the HER. Herein, we studied the doping of late first-row transition metals on the B₁₂P₁₂ and Al₁₂P₁₂ nano-cages as SACs via density functional theory (DFT) calculations. Results show that all transition metals are chemisorbed on the support, with interaction energies ranging from −0.65 to −3.85 eV. The calculated Gibbs free energies of hydrogen evolution are −0.01, −0.06 and −0.20 eV for Ni@Al₁₂P₁₂, Ni@B₁₂P₁₂, and Co@B₁₂P₁₂, respectively, which are close to the optimum value of 0.00 eV, and comparable to the highly active Pt-based catalysts in literature. Our results indicate that the designed Ni@Al₁₂P₁₂, Ni@B₁₂P₁₂, and Co@B₁₂P₁₂ SACs are excellent candidates as noble metal-free, sufficiently stable, and highly efficient electrocatalysts for HER.     

Accessible active sites activated by nano cobalt antimony oxide @ carbon nanotube composite electrocatalyst for highly enhanced hydrogen evolution reaction

The electrochemical hydrogen evolution reaction (HER) was one of new energy development strategies with clean, efficient and renewable characteristics, and electrocatalysts play a crucial role in HER technology. Herein, a composite material (CSO@0.5CNT) derived from the combination of nano cobalt antimony oxide (CSO) with carbon nanotubes (CNT) through hydrothermal reaction, in which the nanoparticles of CSO were closely compounded on the surface of CNT, could be a highly efficient electrocatalyst for HER in 1 M KOH. The binary composite electrocatalyst of CSO and CNT reduced the internal resistance, promoted the charge transfer, exhibited a large electrochemical active area, and obtained the lower overpotential, with 155 mV at 10 mA/cm² current density. Moreover, such a CSO@0.5CNT electrocatalyst displayed a small Tafel slope of 86.5 mV dec^?1, excellent catalytic activity and extraordinary long-term structural stability after 30 h and 3000 CV cycles. Furthermore, the electrocatalytic mechanism revealed by Density Functional Theory (DFT) calculation proved that, the decomposition of H₂O molecules was the control step of the whole HER, and the superior electron transport ability of CNT was favorable to the improvement of electrocatalytic performance. Benefitting from accessible active sites on carbon nanotube (C atom) and CSO (Co atom), the composite electrocatalyst of CSO@0.5CNT displayed synergistic effect for electrocatalytic HER properties, and that was the main mechanism for significantly improving the electrocatalytic activities. Our work provides a novel strategy towards high-efficiency electrocatalysts for hydrogen evolution reaction.     

The CdS/CaTiO3 cubic core-shell composite towards enhanced photocatalytic hydrogen evolution and photodegradation

The CdS/CaTiO₃ cubic core-shell composite is synthesized via a hydrothermal-chemical method. The CdS/CaTiO₃ cubic core-shell composite (CdS/CTO-2) exhibits remarkable photocatalytic HER activity (∼1025.27 μmol·g⁻¹ h⁻¹) and photodegradation enhancement than that of single CaTiO₃ (∼21 folds of HER, ∼19 folds of photodegradation) and single CdS (∼15 folds of HER, ∼15 folds of photodegradation), and a decent stability. There, CdS/CaTiO₃ composite with appropriate potential gradient and CdS with better visible light response can improve carrier efficiency, including increasing carrier transportation, prolonging lifetime and decreasing recombination. Additionally, cubic core-shell microstructure can increase active sites, while maintaining photocatalytic stability.     

Facial synthesis of p-p heterojunction composites: Evaluation of their electrochemical properties with photovoltaics-electrolyzer water splitting using two-electrode system

Mixed transition metal oxides have garnered widespread interest as alternative electrocatalysts for the oxygen and hydrogen generation reactions; however, they tend to require extended synthetic routes, in addition to possessing limited electrocatalytic activities and stabilities. Herein, we report the observation of a synergistic effect between the non-precious metal oxides Mn₃O₄ and Co₃O₄ with CuO and NiO, wherein the resulting composites exhibit promising properties as catalysts for the alkaline water electrolysis process. The activities of these composites in both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) were improved compared to their counterparts, and the dynamic potentials of these processes were reduced. Importantly, low overpotentials of 202 and 380 mV were found for the CuO–Mn₃O₄ composite catalysts for the OER and the HER at 10 mA/cm², respectively. In addition, electrochemical impedance spectroscopy measurements showed a reduced impedance response for the composites, which was dominated by the relaxation of the intermediate frequency associated with the adsorption of the intermediate. Furthermore, the superior catalytic activities of the composites were attributed to their structural properties, high electroactive surface areas, fast electron transport kinetics, and good chemo-electrical bonding between Mn₃O₄ and CuO. Importantly, merging with a marketable silicon-based solar cells, the accumulated PV-EC water splitting device obtains greater hydrogen production under stimulated solar light irradiation. This work offers a typical demonstration and respected strategies for practical large-scale solar H₂ production via an economical PV-EC technology.     

The enhancement of magnetic field assisted water electrolysis hydrogen production from the compact disc recordable waste polycarbonate layer

E-waste is growing rapidly in today's data technology era while the need for green energy is critical. Current compact disc recordable (CD-R) e-waste utilization for hydrogen production by electrolysis is still classified as gray hydrogen production. This study aims to synthesize electrocatalyst for green hydrogen production from CD-R polycarbonate layer. The elemental and morphological characterizations were performed in this study along with molecular dynamics simulation and direct electrolysis experiment. The electrolysis test results shows EMF and high Bisphenol-A (BPA) content from 3 g polycarbonate produce 26000 ppm H₂ almost tripled the EMF only with 10000 ppm H₂ and doubled the EMF with 1 g polycarbonate 15000 ppm H₂. EMF and BPA cooperatively reduces water ionization energy through diamagnetic response and aromatic resonance which vibrates water molecule. Following that, the EMF slowed down OH⁻ ion movement causes the H⁺ movement towards electron become unrestricted. In conclusion, the EMF-BPA cooperation increases hydrogen evolution reaction (HER) through water ionization energy reduction and ion transfer modification.     

An ultra-sensitive dual-signal ratio electrochemical aptasensor based on functionalized bimetallic MOF nanocomplexes by the in-situ electrochemical synthesis for detect HER2

Ratiometric electrochemical biosensors have attracted the attention of researchers due to their ability to self-calibrate, which can improve accuracy of the detection. We constructed a radiometric electrochemical aptasensor based on functionalized bimetallic Zn–Co-MOF@ferrocene (Fc) and Fe–Co-MOF@methylene blue (MB) composites with high specific surface area, high electrical conductivity and strong adsorption properties to detect human epidermal growth factor receptor 2 (HER2). In this paper, we synthesized bimetallic Zn–Co-MOF@Fc by in situ electrochemical synthesis and bimetallic Fe–Co-MOF, and the MB signal was wrapped in Fe–Co-MOF, making it immune to the interference of the external environment. In addition, bimetallic MOFs can also immobilize aptamer on their surfaces through adsorption. Therefore, we used Zn–Co-MOF@Fc/aptamer as the capture probe for HER2 and Fe–Co-MOF@MB as the signal labeling probe to jointly construct the radiometric electrochemical aptasensor. By calculating the ratio of signal peaks, simple, fast and accurate detection of HER2 is achieved. The linear range of the sensor is 0.75–250 pg/mL, and the detection limit is 0.37 pg/mL. It provides a new idea for the detection of breast cancer tumor biomarkers.     

Ni(II) supramolecular gel-derived Ni(0) nanoclusters decorated with optimal N,O-doped graphitized carbon as bifunctional electrocatalysts for oxygen and hydrogen evolution reactions

Developing bifunctional, inexpensive and scalable electrocatalyst for both oxygen and hydrogen evolution reactions (OER and HER) is of essence, considering the thrust for clean fuel hydrogen, and the association of OER with several renewable energy systems, including metal-air batteries. A systematic understanding of electrocatalysts based on the amount and speciation of heteroatom doping on the carbon matrix is fundamental to catalyst design, but remains rarely investigated. This work presents the controlled synthesis of a series of homogeneously dispersed Ni nanoclusters confined in multiple layers of heteroatom-doped graphitized carbon, from the pyrolysis of a readily preparable Ni(II)-triazole gel. The best catalyst showed superior activity requiring low overpotentials of 360 mV & 250 mV and Tafel slopes of 69 mV dec^?1 & 115 mV dec^?1 for OER and HER respectively, with prolonged stability under challenging electrocatalytic conditions. Judicious modulation of the type of heteroatom dopants on Ni@N,O-doped carbon redistributed the electron-density and provided additional active sites, which assisted the adsorption/desorption of OER and HER intermediates during electrocatalysis and improved electron conductivity, benefitting both OER and HER. Our results highlight a simplistic approach for the meticulous synthesis of bifunctional electrocatalysts from supramolecular metallogels, opening new horizons for designing materials for energy applications.     

Advanced Catalyst for CO2 Photo-Reduction: From Controllable Product Selectivity by Architecture Engineering to Improving Charge Transfer Using Stabilized Au Clusters

Despite enormous progress and improvement in photocatalytic CO₂ reduction reaction (CO₂RR), the development of photocatalysts that suppress H₂ evolution reaction (HER), during CO₂RR, remains still a challenge. Here, new insight is presented for controllable CO₂RR selectivity by tuning the architecture of the photocatalyst. Au/carbon nitride with planar structure (p Au/CN) showed high activity for HER with 87% selectivity. In contrast, the same composition with a yolk@shell structure (Y@S Au@CN) exhibited high selectivity of carbon products by suppressing the HER to 26% under visible light irradiation. Further improvement for CO₂RR activity was achieved by a surface decoration of the yolk@shell structure with Au₂₅(PET)₁₈ clusters as favorable electron acceptors, resulting in longer charge separation in Au@CN/Au_c Y@S structure. Finally, by covering the structure with graphene layers, the designed catalyst maintained high photostability during light illumination and showed high photocatalytic efficiency. The optimized Au@CN/Au_c/G Y@S structure displays high photocatalytic CO₂RR selectivity of 88%, where the CO and CH₄ generations during 8 h are 494 and 198 µmol/gcat., respectively. This approach combining architecture engineering and composition modification provides a new strategy with improved activity and controllable selectivity toward targeting applications in energy conversion catalysis.