Abdulmohsen Ali Alshehri

To restore the natural nitrogen cycle (N-cycle), artificial N-cycle electrocatalysis with flexibility, sustainability, and compatibility can convert intermittent renewable energy (e.g., wind) to harmful or value-added chemicals with minimal carbon emissions. The background of such N-cycles, such as nitrogen fixation, ammonia oxidation, and nitrate reduction, is briefly introduced here. The discussion of emerging nanostructures in various conversion reactions is focused on the architecture/compositional design, electrochemical performances, reaction mechanisms, and instructive tests. Energy device advancements for achieving more functions as well as in situ/operando characterizations toward understanding key steps are also highlighted. Furthermore, some recently proposed reactions as well as less discussed C–N coupling reactions are also summarized. We classify inorganic nitrogen sources that convert to each other under an applied voltage into three types, namely, abundant nitrogen, toxic nitrate (nitrite), and nitrogen oxides, and useful compounds such as ammonia, hydrazine, and hydroxylamine, with the goal of providing more critical insights into strategies to facilitate the development of our circular nitrogen economy.

Seawater electrolysis is an extremely attractive approach for harvesting clean hydrogen energy, but detrimental chlorine species (i.e., chloride and hypochlorite) cause severe corrosion at the anode. Here, we report our recent finding that benzoate anions-intercalated NiFe-layered double hydroxide nanosheet on carbon cloth (BZ-NiFe-LDH/CC) behaves as a highly efficient and durable monolithic catalyst for alkaline seawater oxidation, affords enlarged interlayer spacing of LDH, inhibits chlorine (electro)chemistry, and alleviates local pH drop of the electrode. It only needs an overpotential of 320 mV to reach a current density of 500 mA·cm^–2 in 1 M KOH. In contrast to the fast activity decay of NiFe-LDH/CC counterpart during long-term electrolysis, BZ-NiFe-LDH/CC achieves stable 100-h electrolysis at an industrial-level current density of 500 mA·cm^–2 in alkaline seawater. <i>Operando</i> Raman spectroscopy studies further identify structural changes of disordered <i>δ</i> (Ni^III-O) during the seawater oxidation process.

Abstract Electrochemical reduction of NO not only offers an attractive alternative to the Haber–Bosch process for ambient NH 3 production but mitigates the human‐caused unbalance of nitrogen cycle. Herein, we report that MoS 2 nanosheet on graphite felt (MoS 2 /GF) acts as an efficient and robust 3D electrocatalyst for NO‐to‐NH 3 conversion. In acidic electrolyte, such MoS 2 /GF attains a maximal Faradaic efficiency of 76.6 % and a large NH 3 yield of up to 99.6 μmol cm −2 h −1 . Using MoS 2 nanosheet‐loaded carbon paper as the cathode, a proof‐of‐concept device of Zn‐NO battery was assembled to deliver a discharge power density of 1.04 mW cm −2 and an NH 3 yield of 411.8 μg h −1 mg cat. −1 . Calculations reveal that the positively charged Mo‐edge sites facilitate NO adsorption/activation via an acceptance–donation mechanism and disfavor the binding of protons and the coupling of N−N bond.

Abstract NiCo 2 O 4 nanowire array on carbon cloth (NiCo 2 O 4 /CC) is proposed as a highly active electrocatalyst for ambient nitrate (NO 3 − ) reduction to ammonia (NH 3 ). In 0.1 m NaOH solution with 0.1 m NaNO 3 , such NiCo 2 O 4 /CC achieves a high Faradic efficiency of 99.0% and a large NH 3 yield up to 973.2 µmol h −1 cm −2 . The superior catalytic activity of NiCo 2 O 4 comes from its half‐metal feature and optimized adsorption energy due to the existence of Ni in the crystal structure. A Zn‐NO 3 − battery with NiCo 2 O 4 /CC cathode also shows a record‐high battery performance.

NiFeS nanosheet array on Ni foam (NiFeS/NF) behaves as a superb bifunctional electrocatalyst for overall seawater splitting, attaining a commercially demanded current density of 500 mA cm −2 at a low cell voltage of 1.85 V with robust stability.