A high CO ₂ to CO electroreduction rate exceeding 300 mA cm ⁻² was achieved with single atom nickel and nitrogen doped three-dimensional porous carbon electrocatalysts.

A versatile use of a sulfur self‐doped biochar derived from Camellia japonica (camellia) flowers is demonstrated as a multifunctional catalyst for overall water splitting and a supercapacitor. The native sulfur content in the camellia flower facilitates in situ self‐doping of sulfur, which highly activates the camellia‐driven biochar (SA‐Came) as a multifunctional catalyst with the enhanced electron‐transfer ability and long‐term durability. For water splitting, an SA‐Came‐based electrode is highly stable and shows reaction activities in both hydrogen and oxygen evolution reactions, with overpotentials of 154 and 362 mV at 10 mA cm⁻², respectively. For supercapacitors, SA‐Came achieves a specific capacitance of 125.42 F g⁻¹ at 2 A g⁻¹ and high cyclic stability in a three‐electrode system in a 1 M KOH electrolyte. It demonstrated a high energy density of 34.54 Wh kg⁻¹ at a power density of 1600 W kg⁻¹ as a symmetric hybrid supercapacitor device with a wide working potential range of 0–1.6 V.

Ammonia is considered as an alternative fuel resource for a sustainable green future. The production of ammonia involves the electrochemical nitrogen reduction reaction (NRR), which has gained considerable attention due to its eco-friendly resources and nonharmful byproducts. Even with the manifold works on NRR, the technique has not reached the industrial scale because of the impediments of NRR electrocatalysts, and in addition, state-of-the-art electrocatalysts have not yet been discovered. In this review, first, the mechanism of the NRR, key metrics, and operational procedures for NRR electrochemistry are presented. Then, the electrocatalyst designs for efficient NRR are briefly introduced, followed by a discussion on the influence of the electrolytes that enhance NRR performance. The counterion effects of electrolytes on NRR performance and strategies for suppressing the HER by electrolyte additives are also discussed. Later, the NRR mechanisms are upgraded, and a comprehensive review of metal-N₂ batteries is provided. This review summarizes the effective methods for performing the NRR and strategies to suppress the HER on various electrocatalysts by tuning electrolytes and their additives. The review concludes by discussing the prospects of metal-N₂ batteries. Graphical Abstract

This review summarizes recent advances in synthesis strategies, structural engineering, and unique properties of transition metal nitrides, along with the critical discussion on electrode designs for supercapacitors to meet commercial standards.