It is of essential importance to design an electrocatalyst with excellent performance for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in water splitting. Co₃O₄ has been developed as a highly efficient OER electrocatalyst, but it has almost no activity for HER. In a previous study, it has been demonstrated that the formation of oxygen vacancies (V_O) in Co₃O₄ can significantly enhance the OER activity. However, the stability of V_O needs to be considered, especially under the highly oxidizing conditions of the OER process. It is a big challenge to stabilize the V_O in Co₃O₄ while reserving the excellent activity. Filling the oxygen vacancies with heteroatoms in the V_O-rich Co₃O₄ may be a smart strategy to stabilize the V_O by compensating the coordination numbers and obtain an even surprising activity due to the modification of electronic properties by heteroatoms. Herein, we successfully transformed V_O-rich Co₃O₄ into an HER-OER electrocatalyst by filling the in situ formed V_O in Co₃O₄ with phosphorus (P-Co₃O₄) by treating Co₃O₄ with Ar plasma in the presence of a P precursor. The relatively lower coordination numbers in V_O-Co₃O₄ than those in pristine Co₃O₄ were evidenced by X-ray adsorption spectroscopy, indicating that the oxygen vacancies were created after Ar plasma etching. On the other hand, the relatively higher coordination numbers in P-Co₃O₄ than those in V_O-Co₃O₄ and nearly same coordination number as that in pristine Co₃O₄ strongly suggest the efficient filling of P in the vacancies by treatment with Ar plasma in the presence of a P precursor. The Co–O bonds in Co₃O₄ consist of octahedral Co³⁺(O_h)–O and tetrahedral Co²⁺(T_d)–O (Oh, octahedral coordination by six oxygen atoms and T_d, tetrahedral coordination by four oxygen atoms). More Co³⁺(O_h)–O are broken when oxygen vacancies are formed in V_O-Co₃O₄, and more electrons enter the octahedral Co 3d orbital than those entering the tetrahedral Co 3d orbital. Then, with the filling of P in the vacancy site, electrons are transferred out of the Co 3d states, and more Co²⁺(T_d) than Co³⁺(O_h) are left in P-Co₃O₄. These results suggest that the favored catalytic ability of P-Co₃O₄ is dominated by the Co²⁺(T_d) site. P-Co₃O₄ shows superior electrocatalytic activities for HER and OER (among the best non-precious metal catalysts). Owing to its superior efficiency, P-Co₃O₄ can directly catalyze overall water splitting with excellent performance. The theoretical calculations illustrated that the improved electrical conductivity and intermediate binding by P-filling contributed significantly to the enhanced HER and OER activity of Co₃O₄.

Lithium‐ion batteries (LIBs) with higher energy density are very necessary to meet the increasing demand for devices with better performance. With the commercial success of lithiated graphite, other graphite intercalation compounds (GICs) have also been intensively reported, not only for LIBs, but also for other metal (Na, K, Al) ion batteries. In this Progress Report, we briefly review the application of GICs as anodes and cathodes in metal (Li, Na, K, Al) ion batteries. After a brief introduction on the development history of GICs, the electrochemistry of cationic GICs and anionic GICs is summarized. We further briefly summarize the use of cationic GICs and anionic GICs in alkali ion batteries and the use of anionic GICs in aluminium‐ion batteries. Finally, we reach some conclusions on the drawbacks, major progress, emerging challenges, and some perspectives on the development of GICs for metal (Li, Na, K, Al) ion batteries. Further development of GICs for metal (Li, Na, K, Al) ion batteries is not only a strong supplement to the commercialized success of lithiated‐graphite for LIBs, but also an effective strategy to develop diverse high‐energy batteries for stationary energy storage in the future.

The unstable electrode/electrolyte interface with inhomogeneous Zn deposition and side reactions plagues the practical application of aqueous Zn-ion batteries. Herein, L-carnitine (L-CN) is proposed to stabilize both electrodes and extend the lifespan as an efficient additive. Simultaneous quaternary ammonium cations, COO⁻ anions and hydroxyl groups in a trace amount of added L-CN have a huge synergy in manipulating the behaviors of Zn²⁺ electrochemical deposition/insertion and water molecule activity. Specifically, to accommodate the negative charge on electrodes driven by the electric field, the cationic portion in L-CN automatically orients toward the corresponding electrode surfaces (anode for charging and cathode for discharging), occupying active water sites and realizing reversible adsorption interfaces. The carboxyl anion provides a prominent interaction with Zn²⁺, regulating the Zn²⁺ flux to ensure uniform and fast charge transfer kinetics. Hydroxyl groups effectively capture free-water and coordinated-water through hydrogen bond fixation, thus suppressing side reactions and the cathode dissolution. Noticeably, a trace amount of L-CN additive actualizes ultralong life in the symmetric cell with an 87-fold improvement in cycle life (over 6000 h, 1 mA cm⁻²/1 mA h cm⁻²) for dendrite-free Zn plating/stripping and enables the Zn//V₂O₅ full cell to achieve 3500 cycles with a high capacity retention.

This review overviews the recent development of nanomaterials for the application of electrochemical non-enzymatic glucose biosensors. The electrocatalytic mechanism and glucose sensing performance of a variety of nanostructured materials including metallic nanoparticles, metal oxides, metal complexes, alloys and carbon nanomaterials are discussed. The merits and shortfalls of each nanomaterial as electrocatalyst for non-enzymatic biosensing are evaluated and the prospects of non-enzymatic glucose biosensors are presented.