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Developing robust nonprecious electrocatalysts towards hydrogen/oxygen evolution reactions is crucial for widespread use of electrochemical water splitting in hydrogen production. Here, we report that intermetallic Co3Mo spontaneously separated from hierarchical nanoporous copper skeleton shows genuine potential as highly efficient electrocatalysts for alkaline hydrogen/oxygen evolution reactions in virtue of in-situ hydroxylation and electro-oxidation, respectively. The hydroxylated intermetallic Co3Mo has an optimal hydrogen-binding energy to facilitate adsorption/desorption of hydrogen intermediates for hydrogen molecules. Associated with high electron/ion transport of bicontinuous nanoporous skeleton, nanoporous copper supported Co3Mo electrodes exhibit impressive hydrogen evolution reaction catalysis, with negligible onset overpotential and low Tafel slope (~40 mV dec−1) in 1 M KOH, realizing current density of −400 mA cm−2 at overpotential of as low as 96 mV. When coupled to its electro-oxidized derivative that mediates efficiently oxygen evolution reaction, their alkaline electrolyzer operates with a superior overall water-splitting output, outperforming the one assembled with noble-metal-based catalysts. Electrochemical water splitting is an attractive energy conversion technology, but it usually suffers from low efficiency. Here, the authors report intermetallic Co3Mo integrated on porous Cu as highly efficient electrocatalysts for alkaline HER/OER due to in-situ hydroxylation and electro-oxidation.

The hydrogen evolution reaction (HER) is a crucial step in alkaline water electrolysis, but suffers from sluggish reaction kinetics, which calls for the development of active and robust catalysts for the highly efficient production of high-purity hydrogen. Here, we report hierarchical nanoporous (NP) transition-metal (TM = Fe, Co)-doped Pt3Al intermetallic compounds, which are composed of surface alloys of Pt and TMs with in situ self-grown TM hydroxides in an alkaline environment, NP (Pt1−xTMx)3Al/Pt-TM(OH), as highly efficient bifunctional catalysts for the HER. By virtue of the constituent Co(OH)2 having moderate hydroxyl adsorption to accelerate water dissociation and the Pt atoms facilitating the adsorption/desorption of reactive hydrogen intermediates, the NP (Pt1−xCox)3Al/Pt-Co(OH)2 exhibits superior HER activity in 0.1 M KOH, with a low Tafel slope of 48 mV dec−1 and an overpotential of ∼43 mV at 10 mA cm−2, as well as exceptional durability due to its unique nanoporous structure with stable intermetallic bonds. These electrocatalytic properties outperform state-of-the-art Pt-based catalysts, suggesting that multi-site design is suitable for producing highly efficient catalysts towards the HER in alkaline environments.

Designing highly active and robust platinum-free electrocatalysts for hydrogen evolution reaction is vital for large-scale and efficient production of hydrogen through electrochemical water splitting. Here, we report nonprecious intermetallic Cu 5 Zr clusters that are in situ anchored on hierarchical nanoporous copper (NP Cu/Cu 5 Zr) for efficient hydrogen evolution in alkaline medium. By virtue of hydroxygenated zirconium atoms activating their nearby Cu-Cu bridge sites with appropriate hydrogen-binding energy, the Cu 5 Zr clusters have a high electrocatalytic activity toward the hydrogen evolution reaction. Associated with unique architecture featured with steady and bicontinuous nanoporous copper skeleton that facilitates electron transfer and electrolyte accessibility, the self-supported monolithic NP Cu/Cu 5 Zr electrodes boost violent hydrogen gas release, realizing ultrahigh current density of 500 mA cm -2 at a low potential of -280 mV versus reversible hydrogen electrode, with exceptional stability in 1 M KOH solution. The electrochemical properties outperform those of state-of-the-art nonprecious metal electrocatalysts and make them promising candidates as electrodes in water splitting devices.

Designing highly active and robust electrocatalysts for oxygen evolution reaction (OER) is crucial for many renewable energy storage and conversion devices. Here, self-supported monolithic hybrid electrodes that are composed of bimetallic cobalt-molybdenum nitride nanosheets vertically aligned on 3D and bicontinuous nanoporous gold (NP Au/CoMoNx ) are reported as highly efficient electrocatalysts to boost the sluggish reaction kinetics of water oxidation in alkaline media. By virtue of the constituent CoMoNx nanosheets having large accessible CoMoOx surface with remarkably enhanced electrocatalytic activity and the nanoporous Au skeleton facilitating electron transfer and mass transport, the NP Au/CoMoNx electrode exhibits superior OER electrocatalysis in 1 m KOH, with low onset overpotential (166 mV) and Tafel slope (46 mV dec-1 ). It only takes a low overpotential of 370 mV to reach ultrahigh current density of 1156 mA cm-2 , ≈140-fold higher than free CoMoNx nanosheets. The electrocatalytic performance makes it an attractive candidate as the OER catalyst in the water electrolysis.