Surface/Interface Engineering of Hierarchical MoO₂/MoNi₄@Ru/RuO₂ Heterogeneous Nanosheet Arrays for Alkaline Water Electrolysis with Fast Kinetics

Abstract

Comprehensive SummaryRealizing the hydrogen economy by water electrolysis is an attractive approach for hydrogen production, while the efficient and stable bifunctional catalysts under high current densities are the bottleneck that limits the half‐cell reactions of water splitting. Here, we propose an approach of hydrothermal and thermal annealing methods for robust MoO2/MoNi4@Ru/RuO2 heterogeneous cuboid array electrocatalyst with multiplying surface‐active sites by depositing a monolayer amount of Ru. Benefiting from abundant MoO2/MoNi4@Ru/RuO2 heterointerfaces on Cu foam, effectively driving the alkaline water splitting with superior hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The synthesized MoO2/MoNi4@Ru/RuO2 has high HER activity, which realizes the working overpotentials of 48 mV at 50 mA cm‐2, further achieving overpotentials of 230 mV for industry‐level 1000 mA cm‐2 in alkaline water electrolysis. Moreover, it also showed an enhanced OER activity than commercial RuO2 with a small overpotential of 280 mV at 200 mA cm‐2 in alkaline media. When building an electrolyzer with electrodes of (‐)MoO2/MoNi4@Ru/RuO2IIMoO2/MoNi4@Ru/RuO2 (+), a cell voltage of 1.63 V, and 1.75 V just requires to support the current density of 200 mA cm‐2 and 500 mA cm‐2 in alkaline water electrolysis, much lower than the electrolyzer of (‐)Pt/CIIRuO2(+). This work demonstrates that MoO2/MoNi4@Ru/RuO2 heterogeneous nanosheet arrays are promising candidates for industrial water electrolysis applications, providing a possibility for the exploration of water electrolysis with a large current density.This article is protected by copyright. All rights reserved.

Free‐Standing Multiscale Porous High Entropy NiFeCoZn Alloy as the Highly Active Bifunctional Electrocatalyst for Alkaline Water Splitting

“…In alkaline media, it is considered that a Tafel slope at the range of 40 to 120 mV·dec –1 corresponds to one Volmer‐ Heyrovsky mechanism for HER. [ 44‐46 ] The Tafel value of NiFeCoZn/ NiZn‐Ni/NF‐24h means its Volmer‐Heyrovsky mechanism during the HER process, suggesting the rate‐determining step is the adsorption/desorption of H on the active sites over the NiFeCoZn HEA. [ 47 ] In addition, under the overpotential of 100 mV, the TOF value of NiFeCoZn/NiZn‐Ni/NF‐24h is calculated to be 0.031 s –1 , which is larger than that of NiZn‐Ni/NF (0.009 s –1 ), indicating the NiFeCoZn HEA layer has superior electrocatalytic activity toward HER.…”