A new phase of 1T-phase platinum oxide exhibits a record acidic HER activity. A mechanism whereby the [Pt–O] active site can be easily attacked by protons to form the Pt–H intermediate state during the HER is proposed.

Designing well-ordered nanocrystal arrays with subnanometre distances can provide promising materials for future nanoscale applications. However, the fabrication of aligned arrays with controllable accuracy in the subnanometre range with conventional lithography, template or self-assembly strategies faces many challenges. Here, we report a two-dimensional layered metastable oxide, trigonal phase rhodium oxide (space group, P-3m1 (164)), which provides a platform from which to construct well-ordered face-centred cubic rhodium nanocrystal arrays in a hexagonal pattern with an intersurface distance of only 0.5 nm. The coupling of the well-ordered rhodium array and metastable substrate in this catalyst triggers and improves hydrogen spillover, enhancing the acidic hydrogen evolution for H2 production, which is essential for various clean energy-related devices. The catalyst achieves a low overpotential of only 9.8 mV at a current density of −10 mA cm−2, a low Tafel slope of 24.0 mV dec−1, and high stability under a high potential (vs. RHE) of −0.4 V (current density of ~750 mA cm−2). This work highlights the important role of metastable materials in the design of advanced materials to achieve high-performance catalysis.

Carbon dots (C-Dots), with unique properties from tunable photoluminescence to biocompatibility, show wide applications in biotechnology, optoelectronic device and catalysis. Chiral C-Dots are expected to have strongly chirality-dependent biological and catalytic properties. For chiral C-Dots, a clear structure and quantitative structure−property relationship need to be clarified. Here, chiral C-Dots were fabricated by electrooxidation polymerization from serine enantiomers. The oxidized serine has a reversed chiral configuration to serine, which leads to the chiral C-Dots possessing inverse handedness compared with their raw materials. Electron circular dichroism spectrum, together with other diverse characterization techniques and theoretical calculations, confirmed that these chiral C-Dots (2−7 nm) have a well-defined primary structure of polycyclic dipeptide and possess a spatial structure with a c-axis of hexagonal symmetry and two cyclic dipeptides as the spatial structural unit. These chiral C-Dots also show enantioselective catalytic activity on DOPA enantiomers oxidation.

Conspectus As a new kind of carbon based functional material, carbon dots (CDs) have sparked much interest in recent years. The tunable structure, composition, and morphology of CDs unlocks opportunities to enable diversity in their photoelectrochemical properties, and thus they show great potential in various applications such as biology, catalysis, sensors, and energy storage. Nevertheless, the related understanding of CDs is insufficient at present due to their inherent complexity of microstructure, which involves the intersection of high polymer, bulk carbon, and quantum dot (QD). A good understanding of the underlying mechanism behind the properties of CDs is still a formidable challenge, requiring the integration of robust knowledge from organic chemistry, materials science, and solid state physics. Within this context, discovering more appealing properties, elucidating fundamental factors that affect the properties and proposing effective engineering strategies that can realize specific functions for CDs are now highly pursued by researchers. At the beginning of this Account, the main features of CDs are introduced, where not only the basic structural, compositional and morphological characteristics but also the rich photoelectrochemical properties are elucidated, among which the band gap, chirality, photoinduced potential, and electron sink effect are particularly emphasized. Furthermore, new analysis techniques including transient photoinduced current (TPC), transient photoinduced voltage (TPV), and machine learning (ML) to reveal the unique properties of CDs are described. Then, several appealing strategies that aim to rationally tailor CDs for oriented applications are highlighted. These regulation strategies are morphology modulation (e.g., developing CDs with new geometrical configuration, controlling the particle size), phase engineering (e.g., altering the phase crystallinity, introducing the foreign atoms), surface functionalization (e.g., grafting various types of functional groups), and interfacial tuning (e.g., building CD-based nanohybrids with well-defined interfaces). Although the fundamental investigation of CDs is relatively undeveloped because of their complexity, this does not hinder their wide application. At the same time, exploring the extensive applications of CDs will promote their in-depth understanding. Finally, the chances for building a CD-centered blueprint for sustainable society are explored and challenges for future research in the field of CDs are proposed as follows: (i) the controllable synthesis of CDs with uniform size; (ii) search for novel CDs with unique structure, morphology, or composition; (iii) quantitative understanding of the property of CDs; (iv) performance enhancement by external forces such as magnetism or heat injection; (v) construction of the dual carbon concept; (vi) further research on different photocatalytic applications. On the whole, this Account may provide meaningful references for the understanding of the microstructure–property correlation as w...

Direct electrosynthesis of hydrogen peroxide (H2O2) via two‐electron pathway oxygen reduction reaction (2e− ORR) is crucially essential for a sustainable green economy. However, catalysts inevitably undergo four‐electron pathway oxygen reduction reaction (4e− ORR), resulting in low selectivity and economic benefits. The current challenge is to provide a feasible design strategy for obtaining satisfactory 2e− ORR catalysts with high selectivity. In this work, carbon dots (CDs) act as a cocatalyst to regulate the electron transport kinetics of In2O3/CDs, and the influence of CDs on the ORR pathways of In2O3/CDs is also studied. The electron transfer kinetics on In2O3/CDs composites are studied and analyzed using the transient photo‐induced voltage (TPV) technology. Combining the TPV results and kinetics analysis, it is shown that the electron transport on the In2O3 interface is obviously weakened after the addition of CDs, resulting in a high H2O2 selectivity. It is also demonstrated that CDs can effectively enhance the selectivity of H2O2, and the H2O2 selectivity of In2O3/CDs–10 is in close proximity to 100%, which is much higher than that of pure In2O3 (72%). This work will provide a new understanding and insight into addressing the challenge of low H2O2 selectivity for 2e− ORR catalysts.