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Oxygen reduction reaction (ORR) plays a pivotal role in electrochemical energy conversion and commodity chemical production. Oxygen reduction involving a complete four-electron (4e−) transfer is important for the efficient operation...

This review outlines the strategies and challenges of the state-of-the-art non-precious group metal-based catalysts toward water electrolysis.

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Rational control of the coordination environment of atomically dispersed catalysts is pivotal to achieve desirable catalytic reactivity. We report the reversible control of coordination structure in atomically dispersed electrocatalysts via ligand exchange reactions to reversibly modulate their reactivity for oxygen reduction reaction (ORR). The CO‐ligated atomically dispersed Rh catalyst exhibited ca. 30‐fold higher ORR activity than the NHx‐ligated catalyst, whereas the latter showed three times higher H2O2 selectivity than the former. Post‐treatments of the catalysts with CO or NH3 allowed the reversible exchange of CO and NHx ligands, which reversibly tuned oxidation state of metal centers and their ORR activity and selectivity. DFT calculations revealed that more reduced oxidation state of CO‐ligated Rh site could further stabilize the *OOH intermediate, facilitating the two‐ and four‐electron pathway ORR. The reversible ligand exchange reactions were generalized to Ir‐ and Pt‐based catalysts.

H2O2 electrosynthesis is an emerging clean chemical technology, whose efficiency critically depends on the activity and selectivity of electrocatalysts for two-electron oxygen reduction reaction (2e– ORR). Here, we demonstrate that 2e– ORR activity of oxygen-doped carbons, which have been one of the most promising catalysts for this reaction, can be substantially influenced by the types and concentrations of cations in electrolytes. Heat-treated carbon comprising active oxygen functional groups exhibits cation-dependent 2e– ORR activity trends in alkaline media, following the order Cs+ > K+ > Li+. Importantly, an electrolyte with a high cation concentration (0.1 M KOH + 0.5 M KCl) afforded the highest 2e– ORR mass activity (250 ± 30 A gcat –1 at 0.70 V vs reversible hydrogen electrode) ever reported. We have established that the cation promotion effect correlates with cation-dependent electron-transfer kinetics, which regulates the rate-determining first electron transfer to O2.

The hydrogen evolution reaction (HER) is the cathodic half-reaction of water electrolysers for producing hydrogen (H2) gas in a carbon-neutral manner. In the pursuit of system-level H2 production that occurs...

Ordered mesoporous carbons (OMCs) have attracted considerable interest owingt ot heir broad utility.O MCs reported to date comprise amorphous rod-like or tubular or graphitic rod-like frameworks,which exhibit tradeoffs between conductivity and surface area. Here we report ordered mesoporous carbons constructed with graphitic tubular frameworks (OMGCs) with tunable pore sizes and mesostructures via dual templating,using mesoporous silica and molybdenum carbide as exo-and endo-templates,r espectively.O MGCs simultaneously realize high electrical conductivity and large surface area and pore volume.Benefitting from these features, Ru nanoparticles (NPs) supported on OMGC exhibit superior catalytic activity for alkaline hydrogen evolution reaction and single-cell performance for anion exchange membrane water electrolysis compared to Ru NPs on other OMCs and commercial catalysts.F urther,t he OMGC-based full-carbon symmetric cell demonstrates excellent performances for Li-ion capacitors.