Two-dimensional (2D) covalent organic frameworks (COFs) and their derivatives have been widely applied as electrocatalysts owing to their unique nanoscale pore configurations, stable periodic structures, abundant coordination sites and high surface area. This work aims to construct a non-thermodynamically stable Pt-N₂ coordination active site by electrochemically modifying platinum (Pt) single atoms into a fully conjugated 2D COF as conductive agent-free and pyrolysis-free electrocatalyst for the hydrogen evolution reaction (HER). In addition to maximizing atomic utilization, single-atom catalysts with definite structures can be used to investigate catalytic mechanisms and structure-activity relationships. In this work, in-situ characterizations and theoretical calculations reveal that a nitrogen-rich graphene analogue COF not only exhibits a favorable metal-support effect for Pt, adjusting the binding energy between Pt sites to H* intermediates by forming unique Pt-N₂ instead of the typical Pt-N₄ coordination environment, but also enhances electron transport ability and structural stability, showing both conductivity and stability in acidic environments.

Using the self-templating structure of rice husk (RH), hierarchical porous carbon with high surface area was prepared by carbonization, NaOH-leaching and KOH activation. The formation processes of the hierarchical porous structure were discussed in detail, where the silica in RH plays a crucial role. The rice husk-based hierarchical porous carbon (RHHPC) with a 3D porous structure, was composed of macrochannels, mesopores and micropores both on its surface and inner channels. The RHHPC exhibited a surface area as high as 2804 m² g⁻¹ and a high-level of oxygen-containing groups (with an oxygen content of 9.74 at%). The high surface area, large amount of oxygen-containing groups and unique hierarchical porous structure endow the RHHPC with a high capacitance (278 F g⁻¹ at 0.5 A g⁻¹) and excellent rate capability (77.2% retention at 20 A g⁻¹) in 6 mol L⁻¹ KOH. Furthermore, the symmetric supercapacitor fabricated with RHHPC delivered a high energy density of 7.4 W h kg⁻¹ at a power density of 6195 W kg⁻¹, which reveals the promising application of RHHPC in high-performance supercapacitors.

Bi-functional electrode materials, composed of capacitive activated carbon (AC) and battery electrode materials, possess higher power performance than traditional battery electrode materials. Negative electrodes of lead acid batteries with AC additives (i.e., lead–carbon electrodes) display much better charge acceptance than do traditional lead negative electrodes, and are suitable for energy storage in hybrid electrical vehicles. In this paper, we discuss the electrochemical processes on AC in lead–carbon electrodes. In the charging process of the lead–carbon electrode, lead electrodeposits on AC at potentials higher than the open circuit potential of lead, and the large surface area of AC provides extra active sites for lead electrodeposition and the growth of the electrochemical active surface area of lead. Namely, AC acts as an electron bumper and electron distributor in the charging process of the lead–carbon electrode. Most importantly, at high charge rates, the hydrogen evolution reaction (HER) on AC is prohibited by reversible hydrogen adsorption; and meanwhile the adsorbed hydrogen contributes to the charging process.