We report an efficient template-free synthetic route for the preparation of mesoporous nitrogen-doped graphene (NGE) containing a high weight percentage of pyrrolic nitrogen, good specific surface area and comparable electrochemical oxygen reduction activity as that of the state-of-the-art 40 wt% Pt/C catalyst. The desired coordination of nitrogen in the carbon framework of graphene has been conceived by a mutually assisted redox reaction between graphene oxide (GO) and pyrrole, followed by thermal treatment at elevated temperatures. NGE exhibits a high surface area of 528 m 2 g À1 and a pore diameter of $3 to 7 nm. The heat treatment temperature plays a pivotal role in establishing the desired pyrrolic coordination of nitrogen in graphene for the electrochemical oxygen reduction reaction. The NGE sample obtained after heat treatment at 1000 C (NGE-1000) has 53% pyrrolic nitrogen content compared to the similar samples prepared by treating at low temperatures. Most importantly, NGE-1000 has displayed a significantly low overpotential for oxygen reduction with the onset potential very closely matching that of the commercial 40 wt% Pt/C. It is noteworthy that the reaction involves the desired 4 electron transfer as observed in the case of the Pt based electrocatalysts, leading to a significantly high kinetic current density of 6 mA cm À2 at À0.2 V. Moreover, the fuel tolerance and durability under the electrochemical environment of the NGE catalyst is found to be superior to the Pt/ C catalyst.

Polymeric carbon nitride (CN) has emerged as a promising semiconductor in photoanodes for photoelectrochemical cells (PEC) owing to its suitable electronic structure, tunable band gap, high stability, and low price. However, the poor electron diffusion within the CN layer and hole extraction to the solution still limit its applicability in PECs. Here, we report the fabrication of a CN photoanode with excellent electron diffusion length and remarkable hole extraction properties by careful design of its electronic interfaces. We combine complementary synthetic approaches to grow tightly packed CN layers forming a type-II heterojunction, which results in a CN photoanode with excellent charge-separation, high electronic conductivity, and remarkable hole extraction efficiency. The optimized CN photoanode displays excellent PEC performance,

Electrocatalytic oxidative upgrading of organic molecules is a promising alternative process to water oxidation for clean hydrogen production. Yet, its underlying mechanism is still not fully understood, and suitable low‐cost electrocatalysts with good product selectivity and activity are still sought after. Here, an active NiFeOx‐based catalyst is reported on as a general platform for the electro‐oxidative upgrading of organic molecules through oxygenation and dehydrogenation, with hydrogen coproduction. Detailed mechanistic studies unveil that C–H bond oxidation (with a bond dissociation energy BDEC–H of ≈88–96 kcal mol−1) is involved in the rate‐limiting step, which differs significantly from the oxygen evolution reaction mechanism. These findings show that the oxidation efficacy is linearly correlated with the BDEC–H of the molecule. Thus, the catalyst can be used as a general platform for large‐scale electro‐oxidation of various substrates through oxygenation and dehydrogenation at high current density (25 mA cm−2), with a good Faradaic yield. The platform's generality is further demonstrated by the selective oxidation of 5‐(hydroxymethyl)furfural into 2,5‐furandicarboxylic acid with good efficiency.

A simple, straightforward growth method of polymeric carbon nitride (CN) layers on a conductive substrate, with excellent photoelectrochemical activity owing to the formation of a type-II heterojunction by combining two distinct chemical growth methods is reported. The first layer consists of CN prepared from the calcination of a melem-melamine (MeM) adduct; the utilization of MeM enables the preparation of a processable paste which can be easily cast on the conductive substrate. To prepare the second layer, melamine vapor is introduced during calcination. After calcination, two well-connected CN layers with different electronic properties are formed, leading to the formation of a type-II heterojunction. The new CN films exhibit excellent photoelectrochemical properties with a photocurrent density up to 383 μA cm -2 at 1.23 V vs. RHE as well as an acceptable stability over 9 h in 10% (v/v) TEOA-containing 0.1 M KOH aqueous solution, thanks to the enhanced charge separation under illumination. Moreover, the CN films demonstrate good photoelectrochemical activity over a wide pH range, with photocurrent densities of 133, 80, and 118 μA cm -2 in 0.1 M KOH, 0.1 M Na2SO4, and 0.5 M H2SO4 aqueous solutions in the absence of any sacrificial agent, respectively.

Carbon nitrides (CN) have emerged as promising photoanode materials for water-splitting photoelectrochemical cells (PECs). However, their poor charge separation and transfer properties, together with slow wateroxidation kinetics, have resulted in low PEC activity and instability, which strongly impede their further development. In this work, these limitations are addressed by optimizing the charge separation and transfer process. To this end, a nickel-iron based metal-organic framework, Ni/Fe-MIL-53, is deposited, that acts as an oxygen evolution pre-catalyst within the CN layer and incorporate reduced graphene oxide as an electron acceptor. Upon electrochemical activation, a uniform distribution of highly active oxygen evolution reaction (OER) catalysts is obtained on the porous CN surface. Detailed mechanistic studies reveal excellent hole extraction properties with high OER catalytic activity (83% faradaic efficiency) and long-term stability, up to 35 h. These results indicate that the decrease in performance is mainly due to the slow leaching of the catalyst from the CN layer. The CN photoanode exhibits a reproducible photocurrent density of 472 ± 20 µA cm −2 at 1.23 V versus reversible hydrogen electrode (RHE) in 0.1 m KOH, an exceptionally low onset potential of ≈0.034 V versus RHE, and high external quantum yield.