Stable and efficient seawater splitting on a porous phosphate-intercalated NiFe (oxy)hydroxide@NiMoO4 core-shell micropillar electrode

Abstract

Seawater splitting powered by solar or wind sources is a significant renewable energy storage technology for the production of green hydrogen energy. However, both the chlorine evolution reaction and chloride corrosion are intractable issues in seawater splitting. Here, a porous electrode based on a phosphate-intercalated NiFe (oxy)hydroxide shell coated on a nickel molybdate (NiMoO4) micropillar core (denoted as P-NiFe@NiMoO4) is synthesized through an electrochemical oxidation strategy. During the electrochemical oxidation process, the etching of MoO2 promotes the reconstruction of NiFe (oxy)hydroxide and the formation of porous structures in an alkaline solution. The optimized P-NiFe@NiMoO4 electrocatalysts afford a low overpotential of 258 mV at a current density of 100 mA/cm2 in alkaline seawater. By pairing the anode with a cathode of as-synthesized P-NiMoO, the electrolyzer presents a low voltage of 1.63 V at 100 mA/cm2 in alkaline seawater with excellent stability. Moreover, the remarkable stability of the anode seems to be attributed to the in-situ phosphate formed during the electrochemical oxidation process to passivate chloride corrosion.

Facile Fabrication of Bifunctional Hydrogen Catalytic Electrodes for Long-Life Nickel–Hydrogen Gas Batteries

“…The growing energy and climate crisis has driven the development of renewable energy technologies to reduce greenhouse gas emissions and air pollution . Hydrogen energy and reliable large-scale energy storage technologies with low levelized cost of storage (LCOS) are critical for future renewable energy development. − Historically, Ni–H 2 batteries based on the platinum catalytic anode display outstanding durability over 40 000 cycles, which have reliably served aerospace systems for over four decades. − The typical Ni–H 2 battery is composed of a durable Ni­(OH) 2 cathode in conversion reactions of Ni­(OH) 2 /NiOOH and a hydrogen anode in HER/HOR catalytic reactions in strong alkaline electrolytes. , Unlike water splitters and fuel cells, which require very high current densities (>1 A cm –2 ) for HER or HOR, mild current requirements of the Ni–H 2 battery make the hydrogen catalytic anode very durable because it only provides a surface on which the H 2 –H 2 O redox reactions can occur. − In addition to the ultralong service life, the Ni–H 2 chemistry possesses excellent characteristics of intrinsic safety and maintenance-free and all-climate attributes. − However, Pt anodes with high loading of 1–10 mg Pt cm –2 are needed in space Ni–H 2 cells due to strict space mission criteria in which the cost is not a major concern. − More importantly, the HER/HOR activities of platinum group metal (PGM) catalysts drop approximately 100-fold when changing the electrolyte from acidic to alkaline …”

SnS2 Monolayer-Supported Transition Metal Atoms as Efficient Bifunctional Oxygen Electrocatalysts: A Theoretical Investigation

“…Fuel cells and water splitting usually involve the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), which are two crucial electrode reaction processes for renewable energy technologies. − It has been reported that Pt, RuO 2 , and IrO 2 are generally regarded as electrocatalysts for OER and ORR. − However, these electrocatalysts are restricted to large-scale applications due to their high price, sluggish kinetic rates, and low selectivity. − Up to now, it is still challenging to explore both inexpensive and high-performance bifunctional OER and ORR electrocatalysts. , Recently, transition metals anchored on the surface of layered metal dichalcogenides (LMDs) hold great potential as OER and ORR catalysts due to their promising properties (low price, nontoxicity, and good stability). ,− For instance, Peng et al demonstrated that Pd@1T-MoS 2 can act as an efficient bifunctional electrocatalyst for OER and ORR in unitized regenerative fuel cells. In addition, the inert in-plane S-atoms of MoS 2 can be activated by introducing the Cu or Co atom, which improves the catalytic activity of MoS 2 for hydrogen and oxygen evolution reactions .…”

In situ growth of Prussian blue analogue-derived Fe-doped NiS on Ni(OH)2 for efficient hydrogen evolution reaction

“…In the Ni 2p core level spectrum, the binding energy difference between Ni 2p 3/2 and Ni 2p 1/2 is approximately equal to 17.7 eV, indicating the existence of Ni(OH) 2 . 28,[33][34][35][36] Besides, the two peaks at 861.6 and 880.1 eV correspond to the shakeup satellite peaks (denoted as sat.). Note that the whole Ni 2p peaks of Fe-NiS/ Ni(OH) 2 /CC shift negatively (0.3 eV) compared to those of NiS/ Ni(OH) 2 /CC, which is probably caused by Fe doping.…”

“…7c shows the high-resolution Fe 2p spectrum. Peaks were observed at 712.0 and 724.8 eV, attributed to Fe 2p 3/2 and Fe 2p 1/2 for Fe 3+ , respectively, 29,34,42 implying that most Fe exists in the form of Fe 3+ . The signals centred at 716.9 are indexed to their satellite peaks.…”