Making highly efficient catalysts for an overall ​water splitting reaction is vitally important to bring solar/electrical‐to‐hydrogen energy conversion processes into reality. Herein, the synthesis of ultrathin nanosheet‐based, hollow MoOx/Ni3S2 composite microsphere catalysts on nickel foam, using ammonium molybdate as a precursor and the triblock copolymer pluronic P123 as a structure‐directing agent is reported. It is also shown that the resulting materials can serve as bifunctional, non‐noble metal electrocatalysts with high activity and stability for the hydrogen evolution reaction (HER) as well as the oxygen evolution reaction (OER). Thanks to their unique structural features, the materials give an impressive water‐splitting current density of 10 mA cm−2 at ≈1.45 V with remarkable durability for >100 h when used as catalysts both at the cathode and the anode sides of an alkaline electrolyzer. This performance for an overall water splitting reaction is better than even those obtained with an electrolyzer consisting of noble metal‐based Pt/C and IrOx/C catalytic couple—the benchmark catalysts for HER and OER, respectively.

The overall water splitting into hydrogen and oxygen is one of the most promising ways to store intermittent solar and wind energy in the form of chemical fuels. However, this process is quite thermodynamically uphill, and thus needs to be mediated simultaneously by efficient hydrogen evolving and oxygen evolving catalysts to get any feasible output from it. Herein, we report the synthesis of such a catalyst comprising ultrasmall Ni x Co 3-x S 4 -decorated Ni 3 S 2 nanosheet arrays supported on nickel foam (NF) via a partial cation exchange reaction between NF-supported Ni 3 S 2 nanosheet arrays and cobalt(II) ions. We show that the as-prepared material, denoted as Ni x Co 3-x S 4 /Ni 3 S 2 /NF, can serve as a selfstanding, noble metal-free, highly active and stable, bifunctional electrocatalyst for the two half reactions involved in the overall water splitting: the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). Furthermore, we demonstrate that a high-performance electrolyzer for the overall water splitting reaction can be assembled by using Ni x Co 3-x S 4 /Ni 3 S 2 /NF as the electrocatalyst at both the cathode and the anode sides of the electrolyzer. This electrolyzer delivers water-splitting current densities of 10 and 100 mA/cm 2 at applied potentials of 1.53 and 1.80 V, respectively, with remarkable stability for >200 h in both cases. The electrolyzer's performance is much better than the performances of electrolyzers assembled from many types of other bifunctional electrocatalysts as catalyst couple. Moreover, the overall performance of the electrolyzer is comparable with the performances of electrolyzers containing two different, benchmark, monofunctional HER and OER electrocatalyst couple (i.e., Pt/C-IrO 2 ). Keywords： Water splitting • Nickel sulfide • Cobalt sulfide • Electrocatalysis • Composite materialDe-jun Wang received his Ph. D. from Jilin University in 1989. He then worked as a Postdoctoral researcher at Kyoto University for 1 year since 1989-1990. In 1992, he joined Jilin University as a staff. He is currently a Professor in the College of Chemistry, Jilin University. His research interests include surface photovoltage technology, photoelectric sensors, photoelectrochemical water splitting and solar cells.

Despite the superior oxygen evolution electrocatalytic activity of metal-selenide nanostructures, especially when compared with their oxide counterparts, the origin behind their excellent activity remains unclear.

Evolution-based deep generative models represent an exciting direction in understanding and designing proteins. An open question is whether such models can represent the constraints underlying specialized functions that are necessary for organismal fitness in specific biological contexts. Here, we examine the ability of three different models to produce synthetic versions of SH3 domains that can support function in a yeast stress signaling pathway. Using a select-seq assay, we show that one form of a variational autoencoder (VAE) recapitulates the functional characteristics of natural SH3 domains and classifies fungal SH3 homologs hierarchically by function and phylogeny. Locality in the latent space of the model predicts and extends the function of natural orthologs and exposes amino acid constraints distributed near and far from the SH3 ligand-binding site. The ability of deep generative models to specify orthologous function in vivo opens new avenues for probing and engineering protein function in specific cellular environments.

T. Asefa, X. Zou, and co‐workers present a nickel foam‐supported, ultrathin nanosheet‐based, hollow Ni3S2‐based electrocatalyst for overall water splitting on page 4839. By using this material as electrocatalyst both at the cathode and the anode sides of an electrolyzer, a water‐splitting efficiency is achieved that outperforms even noble‐metal‐based Pt/C and IrOx/C benchmark electrolyzers. This result represents an important step toward efficient, non‐noble metal electrocatalyst‐based overall water splitting.