An FeV(O) complex has been synthesized from equimolar solutions of (Et4N)2[FeIII(Cl)(biuret-amide)] and mCPBA in CH3CN at room temperature. The FeV(O) complex has been characterized by UV–vis, EPR, Mössbauer, and HRMS and shown to be capable of oxidizing a series of alkanes having C–H bond dissociation energies ranging from 99.3 kcal mol−1 (cyclohexane) to 84.5 kcal mol−1 (cumene). Linearity in the Bell–Evans–Polayni graph and the finding of a large kinetic isotope effect suggest that hydrogen abstraction is engaged the rate-determining step.

Water splitting, leading to hydrogen and oxygen in a process that mimics natural photosynthesis, is extremely important for devising a sustainable solar energy conversion system. Development of earth-abundant, transition metal-based catalysts that mimic the oxygen-evolving complex of photosystem II, which is involved in oxidation of water to O2 during natural photosynthesis, represents a major challenge. Further, understanding the exact mechanism, including elucidation of the role of active metal-oxo intermediates during water oxidation (WO), is critical to the development of more efficient catalysts. Herein, we report Fe(III) complexes of biuret-modified tetra-amidomacrocyclic ligands (Fe-TAML; 1a and 1b) that catalyze fast, homogeneous, photochemical WO to give O2, with moderate efficiency (maximum TON = 220, TOF = 0.76 s(-1)). Previous studies on photochemical WO using iron complexes resulted in demetalation of the iron complexes with concomitant formation of iron oxide nanoparticles (NPs) that were responsible for WO. Herein, we show for the first time that a high valent Fe(V)(O) intermediate species is photochemically generated as the active intermediate for the oxidation of water to O2. To the best of our knowledge, this represents the first example of a molecular iron complex catalyzing photochemical WO through a Fe(V)(O) intermediate.

The mechanistically distinct and synergistic role of phosphite anions in hydrogen evolution and nickel cations in oxygen evolution have been uncovered for active and durable overall water splitting catalysis in nickel phosphite.

Over the years, cobalt phosphates (amorphous or crystalline) have been projected as one of the most significant and promising classes of nonprecious catalysts and studied exclusively for the electrocatalytic and photocatalytic oxygen evolution reaction (OER). However, their successful utilization of hydrogen evolution reaction (HER) and the reaction of overall water-splitting is rather unexplored. Herein, presented is a crystalline cobalt phosphate, Co 3 (OH) 2 (HPO 4 ) 2 , structurally related to the mineral lazulite, as an efficient precatalyst for OER, HER, and water electrolysis in alkaline media. During both electrochemical OER and HER, the Co 3 (OH) 2 (HPO 4 ) 2 nanostructure was completely transformed in situ into porous amorphous CoO x (OH) films that mediate efficient OER and HER with extremely low overpotentials of only 182 and 87 mV, respectively, at a current density of 10 mA cm −2 . When assemble as anode and cathode in a two-electrode alkaline electrolyzer, unceasing durability over 10 days is achieved with a final cell voltage of 1.54 V, which is superior to the recently reported effective bifunctional electrocatalysts. The strategy to achieve more active sites for oxygen and hydrogen generation via in situ oxidation or reduction from a well-defined inorganic material provides an opportunity to develop cost-effective and efficient electrocatalysts for renewable energy technologies.

Electrochemical splitting of water to oxygen and hydrogen using earth-abundant first-row transition metal-based catalysts is a promising approach for sustainable energy conversion. Herein, we present a new convenient synthesis of copper nitride (Cu 3 N) that acts as a bifunctional electro(pre)catalyst for oxygen evolution reaction (OER), hydrogen evolution reaction (HER), and overall water electrolysis in alkaline media. Strikingly, the electrophoretically deposited Cu 3 N on nickel foam (NF) displayed extremely low overpotentials for both OER and HER, and the overall water splitting cell potential was merely 1.62 V with a remarkable durability of over 10 days. Most notably, the coordinatively unsaturated Cu in Cu 3 N transformed in situ under a reducing environment and in an oxidative environment into a copper-rich shell that serves as the active site over an equally important electrically conductive Cu 3 N core to drive proficient catalysis. To the best of our knowledge, this is the first report on copper nitride for efficient and durable alkaline water electrolysis.