In Situ Construction of Ta:Fe₂O₃@CaFe₂O₄ Core–Shell Nanorod p–t–n Heterojunction Photoanodes for Efficient and Robust Solar Water Oxidation

In order to ameliorate the poor charge transfer characteristics of hematite (α-Fe2O3) photoanodes for photoelectrochemical (PEC) water splitting, heterojunction formation with p-CaFe2O4 is attempted. Here, we report the in situ construction of a highly crystalline p-CaFe2O4 shell on the surface of n-Ta:Fe2O3 nanorods to form Ta:Fe2O3@CaFe2O4 core–shell nanorod p–t–n heterojunction photoanodes with a transition layer (t) between them by a combined strategy of hybrid microwave annealing (HMA) and in situ Ta doping. The successful fabrication of the elaborate heterostructure is due to effective crystallization of p-CaFe2O4 by HMA and prevention of Ca diffusion by already doped Ta atoms in hematite. The optimized Ta:Fe2O3@CaFe2O4 photoanode loaded with the FeNiOx cocatalyst achieves a photocurrent density of 2.70 mA cm–2, a low onset potential of 0.63 VRHE, and long-time stability in PEC water oxidation at 1.23 VRHE under 100 mW cm–2 solar irradiation, which represent marked improvements over bare hematite photoanodes and already reported hematite-based heterojunction photoanodes

High-Performance Electrochemical and Photoelectrochemical Water Splitting at Neutral pH by Ir Nanocluster-Anchored CoFe-Layered Double Hydroxide Nanosheets

Highly efficient electrocatalysts for the oxygen evolution reaction (OER) in neutral electrolytes are indispensable for practical electrochemical and photoelectrochemical water splitting technologies. However, there is a lack of good, neutral OER electrocatalysts because of the poor stability when H+ accumulates during the OER and slow OER kinetics at neutral pH. Herein, we report Ir species nanocluster-anchored, Co/Fe-layered double hydroxide (LDH) nanostructures in which the crystalline nature of LDH-restrained corrosion associated with H+ and the Ir species dramatically enhanced the OEC kinetics at neutral pH. The optimized OER electrocatalyst demonstrated a low overpotential of 323 mV (at 10 mA cm–2) and a record low Tafel slope of 42.8 mV dec–1. When it was integrated with an organic semiconductor-based photoanode, we obtained a photocurrent density of 15.2 mA cm–2 at 1.23 V versus reversible hydrogen in neutral electrolyte, which is the highest among all reported photoanodes to our knowledge

Highly Efficient Layered Double Hydroxide-Derived Bimetallic Cu–Co Alloy Catalysts for the Reverse Water–Gas Shift Reaction

Bimetallic alloy catalysts with finely controlled composition and atomic mixing of the two active metals are vital for maximizing their synergistic effect in enhancing catalytic performances. Herein, we report the design and synthetic strategy of bimetallic Cu–Co alloy catalysts well dispersed on Al2O3 from a CuCoAl-layered double hydroxide (LDH) for boosting the reverse water–gas shift (RWGS) performance by controlling the composition and textural properties of Cu–Co alloy particles. An optimized Cu9Co1/Al2O3 catalyst exhibits a remarkably high CO2 to CO conversion rate (∼0.247 mol h–1 gcat–1) with ∼99.4% of CO selectivity at a relatively low reaction temperature of 400 °C, which outperforms a monometallic Cu/Al2O3 catalyst and a reference Cu9Co1/Al2O3 catalyst prepared by a conventional impregnation method. A combined experimental and theoretical study reveals that the superior activity of the Cu9Co1/Al2O3 catalyst is attributed to two factors: (i) a modified electronic structure due to the Cu–Co alloy formation that facilitates CO2 activation and CO desorption and (ii) formation of well-dispersed alloy nanoparticles by using LDHs as the catalyst precursors