Water structure near electrode interfaces may play an important role in controlling CO2 electroreduction. Using plasmon-enhanced vibrational sum frequency generation spectroscopy, we demonstrate the emergence of an interfacial water subpopulation with large electric fields along their OH bonds, when Na2CO3 ions are present near the electrode under applied potential. With molecular dynamics simulations, we show that the approach of aqueous Na2CO3 to electrodes is coupled to the formation of structured and oriented ion complexes, and that the emergent water population is associated with the first solvation shell of these complexes. This water subpopulation is seen even when the sole source of CO3 is its in-situ generation from CO2, indicating that the interfacial species investigated here are likely ubiquitous in CO2 electroreduction contexts.
Electrochemical conversion of CO2 on Cu-based catalysts offers an auspicious strategy for addressing the increasingly serious environmental issues. However, there is still a challenge in the regulation of selectivity for an efficient CO2 conversion process on Cu-based catalysts due to the complexity of the internal structure of catalysts. Herein, we step wisely control the intrinsic grain boundaries (GBs) and Sn doping in Cu substrate to optimize the CO2 reduction reaction (CO2RR) performance of catalyst, which also clearly clarify the contribution of above two factors towards CO2RR performance. As a result, the as-synthesized R-SnCu catalyst with both GBs and Sn doing exhibits the highest CO selectivity of 99 % at -0.8 V versus hydrogen electrode (vs. RHE). In-situ Raman spectroscopy was further used to provide critical evidence of the key intermediates during CO2RR. We find that compared to the catalysts containing only GBs or Sn doping, the R-SnCu catalyst controlled by both GBs and Sn doping exhibits a more pronounced adsorption preference for C-bound *COOH intermediate peaks related to CO generation. These findings provide new ideas for the effective design of high-performance Cu-based CO2RR catalysts.
The recombination of photogenerated charges is always a hinder for the improvement of photocatalytic efficiency. Herein, as a case of study, graphitic carbon nitride (g-C3N4) modified with N vacancies and Yb doping (YbCN) was synthesized by the thermal polymerization of ytterbium nitrate and melamine. The optimized sample showed a photocatalytic efficiency of 99.9% within 30 min for degrading tetracycline (TC) under visible light irradiation (lambda > 420 nm), which was 24 times than pure g-C3N4. The experimental results and density functional theory (DFT) calculations support that the enhanced performance for photocatalytic decomposition of TC was attributed to the doped Yb3+ and the formation of N vacancies. The doped Yb3+ and induced polarization can expand the light responsive range and inhibit the recombination of photogenerated carriers. Moreover, the introduction of Yb3+ in g-C3N4 can accelerate the adsorption and activation of O-2 to generate O-1(2), O-center dot(2)- and (OH)-O-center dot. Furthermore, the photocatalytic degradation pathway of TC was revealed by HPLC-MS and DFT calculations. Finally, the optimized sample catalyst was also employed for photocatalytic decomposition of TC in practical conditions including tap, river, and lake water. It was found that inorganic ions in real water can influence the photocatalytic degradation of TC. This work disclosed a strategy for the rational design of efficient g-C3N4-based materials for practical environmental remediation.
Strong metal-support interactions (SMSIs) play a pivotal role in enhancing the catalytic activity and stability of supported metal catalysts in heterogeneous thermal catalysis, but construction of effective SMSIs remains challenging in electrocatalysis. As a ubiquitous and versatile support for electrocatalysts, carbon materials are generally too inert to generate SMSIs with the loaded metal active sites. We hereby report a CVD-based method to prepare Ru nanoparticles on arrays of oxygen-and nitrogen-doped CNTs grown on the fibers of carbon paper (Ru/ONCNT@CP). The SMSIs were manifested by electronic structure tuning of Ru nanoparticles and their partial embedment in the carbon support. The SMSIs result in optimized Gibbs free energy of H*, lowered energy barrier of H2O dissociation, and enhanced catalyst robustness. Combined with the hierarchical microstructure, high surface area and hydrophilic/aerophobic nature, the Ru/ONCNT@CP electrode displays excellent HER catalytic activity in 1 M KOH, requiring overpotentials of only 73, 180, and 252 mV to achieve current densities of 100, 500, and 800 mA cm(-2), respectively. Moreover, the Ru/ONCNT@CP electrode exhibits outstanding stability, with negligible current decay after 120 h HER operation at 100 mA cm(-2). This work features an effective and scalable approach for preparation of metal-loaded-carbon electrocatalysts with engineered microstructure and SMSIs.
Modulation of electric currents through single-molecule junctions is usually achieved by synthesis of molecules with desired functionalities, in conjunction with suitable molecule–electrode contacts through specific anchoring groups. An alternative to this approach, barely explored so far, is to use structured electrodes, where conductivity could eventually be controlled by changing the specific anchoring site within the very same electrode. Here, we theoretically investigate how to exploit the pronounced anisotropy of corrugated graphene deposited on Ru(0001) (Gr/Ru) to tailor single-molecule conductivity in 4-aminophenyl and 4-aminobenzonitrile. We show that currents induced in the upper and lower anchoring positions in the Gr/Ru moiré are substantially different, irrespective of the chosen molecule. The magnitude of these currents can differ by as much as an order of magnitude at specific bias voltages. We also show that both molecules display rectifying properties, which can differ by up to a factor of five in different anchoring sites. Interestingly, the observed modulations strongly depend on the chemical binding nature between the molecule and the electrode, (strong) covalent bond for 4-aminophenyl and (weak) physisorption for 4-aminobenzonitrile. All this suggests that Gr/Ru can be an ideal electrode to modulate single-molecule electric conductivity under experimental conditions that are available in many laboratories.
