Nonprecious transition metal nitrides have attracted considerable attention as an alternative catalyst to noble metals for electrochemical reactions. Titanium nitride (TiN), in particular, is an interesting material that exhibits excellent thermal, chemical, and mechanical stability, electrical conductivity, and in particular electrocatalytic activity. TiN is often prepared by the nitridation of titanium oxide using gaseous ammonia or hydrazine as a nitrogen source. This high temperature synthesis, however, gives a material with low surface area, which is unfavorable for its application in heterogeneous electrocatalysis. The shape and size of the assembly, and thus the resulting g-CN materials, can be tailored simply by using different precipitation temperatures, solvents, and comonomers. Furthermore, the assembly develops unique nanostructures during the polycondensation without losing the pristine macrostructures.

We report utilization of graphitic carbon nitride (g-CN) as an electrocatalyst for dye-sensitized solar cells (DSSCs). Crystalline poly(triazine imide) based g-CN was synthesized via a modified ionothermal method, and deposited onto the counter electrodes along with a conductive additive and a sacrificial polymer binder. The resulting DSSCs exhibited a power conversion efficiency (7.8%) comparable to that of conventional Pt catalyst (7.9%), confirming the excellent catalytic activity of poly(triazine imide) g-CN as a non-precious metal electrocatalyst.

Simple organic cooperative assembly of triazine molecules leads to three-dimensional macroscopic assemblies of low-dimensional graphitic carbon nitrides (g-CNs), for example, nanoparticles, nanotubes, and nanosheets. The approach enables the characterization of the cooperative properties and photocatalytic activities of low-dimensional g-CN materials in hydrogen evolution reactions from water under visible light.

The Li-S system offers a tantalizing battery for electric vehicles and renewable energy storage due to its high theoretical capacity of 1675 mAh g(-1) and its employment of abundant and available materials. One major challenge in this system stems from the formation of soluble polysulfides during the reduction of S8, the active cathode material, during discharge. The ability to deploy this system hinges on the ability to control the behavior of these polysulfides by containing them in the cathode and allowing for further redox. Here, we exploit the high surface areas and good electrical conductivity of mesoporous carbons (MC) to achieve high sulfur utilization while functionalizing the MC with sulfur (S-MC) in order to modify the surface chemistry and attract polysulfides to the carbon material. S-MC materials show enhanced capacity and cyclability trending as a function of sulfur functionality, specifically a 50% enhancement in discharge capacity is observed at high cycles (60-100 cycles). Impedance spectroscopy suggests that the S-MC materials exhibit a lower charge-transfer resistance compared with MC materials which allows for more efficient electrochemistry with species in solution at the cathode. Isothermal titration calorimetry shows that the change in surface chemistry from unfunctionalized to S-functionalized carbons results in an increased affinity of the polysulfide intermediates for the S-MC materials, which is the likely cause for enhanced cyclability.

We propose a nanostructured Mn-doped V2O5 lithium-ion battery cathode material that facilitates cathodic charge transport. The synthesis strategy uses a layered compound, vanadium(III) jarosite, as the precursor, in which the Mn2+ ions are doped uniformly between the vanadium oxide crystal layers. Through a two-step transformation, the vanadium jarosite was converted into Mn2+-doped V2O5. The resulting aliovalent doping of the larger Mn cations in the modified V2O5 structure increases the cell volume, which facilitates diffusion of Li+ ions, and introduces oxygen vacancies that improve the electronic conductivity. Comparison of the electrochemical performance in Li-ion batteries of undoped and the Mn2+-doped V2O5 hierarchical structure made from layered vanadium jarosite confirms that the Mn-doping improves ion transport to give a high cathodic columbic capacity (253 mAhg-1 at 1C, 86% of the theoretical value, 294 mAhg-1) and excellent cycling stability.