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This review summarizes current research progress and future development opportunities of vanadium-based compounds and heterostructures as functional sulfur catalysts for lithium–sulfur batteries.

The electrochemical quartz crystal microbalance (EQCM) and density functional theory (DFT) have been combined to study the special reaction between thiourea (TU) and metal cluster and the mechanism of the replacement of Cu by Sn in the presence of TU for the first time. The natural bond orbital (NBO) charge of the top copper atom obviously shifts toward positive values compared to the interaction behavior of single and double (SC) regions with Cu 4cluster via the DFT method. This can explain the reason for the accelerating corrosion process at higher TU concentrations since the copper atoms can change to cuprous ions in this process. It is proven that the thermodynamically impossible replacement of Cu by Sn can occur in the presence of TU by reducing the OCP of the copper electrode to a more negative value than the redox potential of Sn 2+/Sn. The DFT investigation on the interactions between delocalization (SC) and (NC) regions in TU and Cu 4or Sn 4cluster indicates that the highest molecular occupied orbital (HOMO) of the SC region has better than adequate to the lowest unoccupied molecular orbital (LUMO) of Cu 4cluster than that of Sn 4cluster. The replacement mechanism deduced based on the first-principles analysis is universally applicable to the alloy deposition, corrosion inhibition, and surface treatment.

In this work, the oxidation mechanism of hypophosphite anion ( H2PO2-) in acidic and alkaline media in the presence of Ni(II) specie was investigated by using electrochemical impedance spectroscopy (EIS) and density functional theory (DFT). In EIS, three major electrochemical processes in the electroless deposition process were found, when the solution pH ranged from 5.5 to 9.5. To understand the microscopic mechanisms involved, all participate species in the reaction pathways were calculated by the DFT method along with a natural bond orbital (NBO) analysis. Two emulating reactions were demonstrated:  Path (I) passes through a primary dehydrogenation (D-RP), and Path (II) includes a primary addition of OH-(A-RP) on the hypophosphite anion. By comparison of the energy levels of all species, it can be concluded that Path (II) is energetically favorable under both acidic and alkaline conditions. The DFT and NBO analysis can provide strong evidence for the loops detected in the EIS, especially especially for the inductive loop (IL-M) in the medium-frequency domain that is caused by the formation of NiI−H3PO2(OH) and the capacitive loop (CL-L) in the low-frequency domain by H2PO2(OH). The combination of electrochemical analysis (EIS) and first principle theory (DFT) analysis proves that it is helpful to explore the nature of the interaction between anodic and cathodic reactions in the electroless deposition process.

With the rapid electrochemical development of hydrogen evolution, the search for low‐cost and high activity electrocatalysts for hydrogen evolution has received extensive attention. The fabrication of self‐supported Cu2S‐Cu3P nanowire (Cu2S‐Cu3P NW) arrays on a commercial copper foam by a liquid–solid reaction and subsequent phosphatation at low temperature is reported. The corresponding scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results indicate that the Cu2S‐Cu3P NW arrays have a dense nanowire (NW) structure with sulfur and phosphorous uniformly distributed on the surface of the nanowires. Interestingly, the Cu2S‐Cu3P NW arrays act as a hydrogen‐evolving cathode that when operated in 1.0 mKOH electrolyte only require a low overpotential of 158 mV to achieve a current density of 10 mA cm−2and show a small Tafel slope of 45 mV dec−1. The activity decrease is negligible after holding at −500 mA cm–2for 75 h, which thus demonstrates excellent stability. This could be due to the structure of nanowire arrays and synergistic effects between S and P, which could increase the specific surface area, reduce the charge transfer resistance, facilitate mass diffusion and electron transfers, and increase the active sites. This work therefore provides a simple method to prepare low‐cost and self‐supported electrocatalysts with high catalytic activity for hydrogen evolution. Self‐supported Cu2S‐Cu3P NW arrays on a commercial copper foam are prepared for the first time; these arrays have a remarkable catalytic activity for HER in alkaline solutions. The self‐supported nanowire arrays structure and co‐doping effects of S and P play important roles in enhancing the catalytic activity for hydrogen evolution.