Recent Advances in Self-Supported Semiconductor Heterojunction Nanoarrays as Efficient Photoanodes for Photoelectrochemical Water Splitting.

Growth of semiconductor heterojunction nanoarrays directly on conductive substrates represents a promising strategy toward high-performance photoelectrodes for photoelectrochemical (PEC) water splitting. By controlling the growth conditions, heterojunction nanoarrays with different morphologies and semiconductor components can be fabricated, resulting in greatly enhanced light-absorption properties, stabilities, and PEC activities. Herein, recent progress in the development of self-supported heterostructured semiconductor nanoarrays as efficient photoanode catalysts for water oxidation is reviewed. Synthetic methods for the fabrication of heterojunction nanoarrays with specific compositions and structures are first discussed, including templating methods, wet chemical syntheses, electrochemical approaches and chemical vapor deposition (CVD) methods. Then, various heterojunction nanoarrays that have been reported in recent years based on particular core semiconductor scaffolds (e.g., TiO2 , ZnO, WO3 , Fe2 O3 , etc.) are summarized, placing strong emphasis on the synergies generated at the interface between the semiconductor components that can favorably boost PEC water oxidation. Whilst strong progress has been made in recent years to enhance the visible-light responsiveness, photon-to-O2 conversion efficiency and stability of photoanodes based on heterojunction nanoarrays, further advancements in all these areas are needed for PEC water splitting to gain any traction alongside photovoltaic-electrochemical (PV-EC) systems as a viable and cost-effective route toward the hydrogen economy.

Disruptive Strategy To Fabricate Three-Dimensional Ultrawide Interlayer Porous Carbon Framework-Supported Prussian Blue Nanocubes: A Carrier for NiFe-Layered Double-Hydroxide toward Oxygen Evolution.

We, for the first time, offer a unique and disruptive strategy to prepare N-doped three-dimensional porous carbon framework-supported well-defined Fe4[Fe(CN)6]3 nanocubes (indicated as PB@N-PCFs). The carbon frameworks hold an ultrawide interlayer spacing of 0.385-0.402 nm for the (002) planes of graphite and ultrahigh graphitization. Furthermore, PB@N-PCFs are used as a carrier to grow NiFe-layered-double-hydroxide nanosheet arrays (denoted as NiFe-LDH/PB@N-PCFs) in situ, where the interlayer spacing for the (002) planes of graphite can be expanded as high as 0.457 nm in the carbon frameworks. Moreover, NiFe-LDH/PB@N-PCFs shows excellent electrocatalytic performance toward oxygen evolution in terms of activity, kinetics, and durability, elegantly rivaling the state-of-the-art RuO2. More profoundly, after 3000 cycle cyclic voltammetry scans, NiFe-LDH/PB@N-PCFs still display far more desirable activity with respect to initial NiFe-LDH/PB@N-PCFs. We believe that the PB@N-PCFs and PB@N-PCFs-based composites with ultrahighly graphitized and large interlayer spacing N-PCFs can find more places in electrochemistry-related applications such as Na/K-ion batteries, electrocatalysis, and electrochemical sensors.

Experimental and Theoretical Insights into Enhanced Hydrogen Evolution over PtCo Nanoalloys Anchored on a Nitrogen-Doped Carbon Matrix.

The identification of synergistic effect of Pt-based alloys on hydrogen evolution reaction (HER) requires a combination of experimental studies and theoretical calculations. Here, we present the construction of uniform PtCo nanoparticles grown on N-doped carbon frameworks via pyrolyzing Pt and Co ions adsorbed polyaniline, whereby the nanostructure of the nanoalloys can be effectively tuned by controlling the calcination temperature. As-prepared PtCo@NC-900 shows the optimal HER performance in 0.5 M H2SO4, resulting in a high mass activity of 4.31 A mgPt-1 and excellent operation durability, which far exceeds that of commercial 20 wt % Pt/C (0.30 A mgPt-1). Density functional theory calculations further reveal that the improved HER activity on PtCo(111) is originated from the strong electronic interaction between Pt and Co with favorable electron transfer, allowing for a more suitable binding strength for hydrogen (i.e., ΔG*H = -0.164 eV) compared with that of pristine Pt(111) (-0.287 eV).