Layered Nickel-Cobalt Oxide Coatings on Stainless Steel as an Electrocatalyst for Oxygen Evolution Reaction

Ag on NiCo Layered Double Hydroxide as Oxygen Evolution Electrocatalyst for Anion Exchange Membrane Water Electrolyzer Under Large Current Densities

A facile and universal strategy is employed to synthesize Ag decorated NiCo layered double hydroxide (LDH) heterogeneous structure for the oxygen evolution reaction (OER). The Ag nanoparticles are deposited on NiCo LDH nanosheets via a spontaneous redox reaction. The synthesized Ag/NiCo LDH achieves an overpotential of 460 mV at a current density of 1 A cm-2 geo, surpassing that of NiCo LDH (722 mV). In an anion exchange membrane water electrolyzer (AEMWE) with Ag/NiCo LDH as the anode and Pt/C as the cathode, the cell can deliver an ultrahigh current density of 5 A cm-2 at a low voltage of 2.10 V. This superior current density is nearly four times larger than that of AEMWEs with other non-precious anode electrocatalysts reported in literature under the same effective area. Furthermore, it exhibits desired durability with no performance decay for over 300 h at 1 A cm-2, which is almost six times longer than that of electrolyzer with an IrO2 anode. Operando electrochemical impedance spectroscopy results reveal that Ag decoration facilitates active site formation and reduces the OER onset potential compared to NiCo LDH. This study showcases a practical approach to designing highly effective and durable OER electrocatalysts in industrial hydrogen production.

Water electrolysis: from textbook knowledge to the latest scientific strategies and industrial developments

Replacing fossil fuels with energy sources and carriers that are sustainable, environmentally benign, and affordable is amongst the most pressing challenges for future socio-economic development. To that goal, hydrogen is presumed to be the most promising energy carrier. Electrocatalytic water splitting, if driven by green electricity, would provide hydrogen with minimal CO2 footprint. The viability of water electrolysis still hinges on the availability of durable earth-abundant electrocatalyst materials and the overall process efficiency. This review spans from the fundamentals of electrocatalytically initiated water splitting to the very latest scientific findings from university and institutional research, also covering specifications and special features of the current industrial processes and those processes currently being tested in large-scale applications. Recently developed strategies are described for the optimisation and discovery of active and durable materials for electrodes that ever-increasingly harness first-principles calculations and machine learning. In addition, a technoeconomic analysis of water electrolysis is included that allows an assessment of the extent to which a large-scale implementation of water splitting can help to combat climate change. This review article is intended to cross-pollinate and strengthen efforts from fundamental understanding to technical implementation and to improve the 'junctions' between the field's physical chemists, materials scientists and engineers, as well as stimulate much-needed exchange among these groups on challenges encountered in the different domains.

Water-Based Electrophoretic Deposition of Ternary Cobalt-Nickel-Iron Oxides on AISI304 Stainless Steel for Oxygen Evolution

Coatings consisting of cobalt, nickel and iron (Co-Ni-Fe) oxides were electrophoretically deposited on AISI 304-type stainless steel using aqueous suspensions without any binder. The synthesis of Co-Ni-Fe oxides was carried out by the thermal decomposition of metal nitrates with various molar ratios at 673 K. Structural and morphological analysis confirmed that the deposited coatings were mainly composed of spinel-type oxides with predominantly round-shaped particles. The prepared electrodes were examined for their electrocatalytic performance in oxygen generation under alkaline conditions. Various electrochemical techniques indicated the influence of iron content on the electrochemical activity of Co-Ni-Fe oxides, with the calculated values of the Tafel constant being in the range of 52–59 mV dec−1. Long-term oxygen generation for 24 h at 1.0 V revealed very good mechanical and electrocatalytic stability of the prepared electrodes, since they were able to maintain up to 98% of their initial activity.

PdAgCu Alloy Nanoparticles Integrated on Three-Dimensional Nanoporous CuO for Efficient Electrocatalytic Nitrogen Reduction under Ambient Conditions

Exploration of catalysts is the primary focus of the electrochemical nitrogen reduction reaction (NRR). However, cost-effective materials are rarely reported. Herein, we report a composite consisting of a three-dimensional nanoporous CuO structure decorated with PdAgCu alloy nanoparticles (abbreviated as PdAgCu/CuO composites) as a highly effective catalyst. Compared with the nanoporous PdAgCu alloy and PdCu/CuO and Cu/CuO composites, PdAgCu/CuO composites exhibit much superior NRR catalytic activity with a high NH₃ production rate of 40.4 μg h^-1 mg_cat^-1. In addition, PdAgCu/CuO composites show good catalytic stability for NRR. The superior NRR performance of PdAgCu/CuO composites can be ascribed to the synergistic effects of metals and metal oxides, which are highly significant for the exploration of efficient catalysts for NRR.