Photo-/electrochemical catalyzed oxidative R 1 -H/R 2 -H cross-coupling with hydrogen evolution has become an increasingly important issue for molecular synthesis. The dream of construction of C−C/C−X bonds from readily available C− H/X−H with release of H 2 can be facilely achieved without external chemical oxidants, providing a greener model for chemical bond formation. Given the great influence of these reactions in organic chemistry, we give a summary of the state of the art in oxidative R 1 -H/R 2 -H cross-coupling with hydrogen evolution via photo/electrochemistry, and we hope this review will stimulate the development of a greener synthetic strategy in the near future.

An environmentally friendly electrochemical protocol about cobalt-catalyzed C-H amination of arenes has been developed, which offers a simple way to access synthetically useful arylamines. In divided cells, a wide variety of arenes and alkylamines are examined to afford C-N formation products without using external oxidants, which avoids the formation of undesired byproducts and exhibits high atom economy. Importantly, the reaction can also be extended to gram level with moderate efficiency. KIE experiments indicate that C-H bond cleavage might not be involved during the rate-limiting step.

Aqueous zinc‐ion batteries (ZIBs) have been considered as prospective alternatives for lithium‐ion batteries, which are able to serve as power sources for next‐generation wearable and flexible devices, owing to the merits of abundant zinc resources and high safety of aqueous electrolyte. However, the lack of suitable cathode materials with flexibility for ZIBs hinders their further application. Herein, a novel cathode material [i.e., MnO2 nanosheet‐assembled hollow polyhedron anchored on carbon cloth (MnO2/CC)] was prepared through a rapid hydrothermal method by using ZIF‐67 as self‐sacrificing template. When tested in an aqueous ZIB, the MnO2/CC delivered a high reversible capacity of 263.9 mAh g−1 at 1.0 A g−1 after 300 cycles, far exceeding those of the commercial MnO2 electrode. More importantly, benefiting from the unique structural advantages, a flexible ZIB assembled based on the MnO2/CC displayed a stable output voltage of 1.53 V and a specific capacity of 91.7 mAh g−1 at 0.1 A g−1 after 30 cycles. It also successfully lit LED bulbs even under different bending angles, showing good flexibility. This research contributes to the development of MnO2‐based cathode materials for high‐performance flexible ZIBs.

Portable water splitting devices driven by rechargeable metal–air batteries or solar cells are promising, however, their scalable usages are still hindered by lack of suitable multifunctional electrocatalysts. Here, a highly efficient multifunctional electrocatalyst is demonstrated, i.e., 2D nanosheet array of Mo‐doped NiCo2O4/Co5.47N heterostructure deposited on nickel foam (Mo‐NiCo2O4/Co5.47N/NF). The successful doping of non‐3d high‐valence metal into a heterostructured nanosheet array, which is directly grown on a conductive substrate endows the resultant catalyst with balanced electronic structure, highly exposed active sites, and binder‐free electrode architecture. As a result, the Mo‐NiCo2O4/Co5.47N/NF exhibits remarkable catalytic activity toward the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), affording high current densities of 50 mA cm−2 at low overpotentials of 310 mV for OER, and 170 mV for HER, respectively. Moreover, a low voltage of 1.56 V is achieved for the Mo‐NiCo2O4/Co5.47N/NF‐based water splitting cell to reach 10 mA cm−2. More importantly, a portable overall water splitting device is demonstrated through the integration of a water‐splitting cell and two Zn–air batteries (open‐circuit voltage of 1.43 V), which are all fabricated based on Mo‐NiCo2O4/Co5.47N/NF, demonstrating a low‐cost way to generate fuel energy. This work offers an effective strategy to develop high‐performance metal‐doped heterostructured electrode.

Carbon monoxide is an abundant and cost-efficient C1 building block for the carbonylation industry. Transition-metal-catalyzed oxidative C–H/C­(X)–H carbonylation with CO provides one of the most straightforward approaches to construct carbonyl compounds. However, the use of stoichiometric oxidants would bring several drawbacks such as high cost and undesired chemical waste. Especially, the explosion limit is a potential safety hazard in oxidative carbonylation using O2 as the oxidant. To overcome these issues, an electrochemical strategy for oxidative C–H/N–H carbonylation has been designed by taking advantage of anodic oxidation to recycle a cobalt catalyst, and H2 is generated at the cathode. The intra- and intermolecular carbonylation products can be achieved with good functional group tolerance in 31%–99% yields. A plausible reaction mechanism involving a CoII/CoIII/CoI catalytic cycle is proposed by the studies of XANES and CV.

An electrocatalytic reaction protocol is developed for achieving intramolecular dehydrogenative annulation of N-aryl enamines. It offers a simple and efficient way for the synthesis of indoles in an undivided cell. Good to excellent yields are obtained under oxidant-free and transition-metal-free conditions. Moreover, imidazo[1,2-a]pyridines could also be produced when N-pyridyl enamines were used as the substrates.

Through iodine catalysis, the direct oxidative coupling/annulation of β-keto esters or 2-pyridinyl-β-esters with alkenes was achieved. This reaction procedure provides a simple and selective way for the synthesis of dihydrofurans and indolizines in one step.

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