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In recent years, as a green renewable energy production technology, electrochemical water splitting has demonstrated high development potential. Many materials have been reported as successful catalysts in the water-splitting field. However, it is still a huge challenge to produce bifunctional electrocatalysts for the efficient and sustainable generation of hydrogen and oxygen simultaneously. Herein, we successfully developed oxygen vacancies abundant CuCo layered double oxide (Ov-CuCo-LDO) hollow nanotube arrays (HNTAs) loaded on nickel foam as advanced electrocatalysts for total water splitting. When the current density was 10 mA cm−2, the Ov-CuCo-LDO HNTAs exhibited outstanding onset overpotentials of 53.9 and 72.5 mV for the hydrogen evolution and oxygen evolution reactions (HER and OER) in alkaline medium, respectively, because of the bimetallic synergistic effect between the cobalt and copper and the unique hollow porous structure. In addition, an as-assembled Ov-CuCo-LDO‖‖Ov-CuCo-LDO electrolytic cell showed a small potential of 1.55 V to deliver a current density of 10 mA cm−2. Moreover, it also showed remarkable durability after long-term overall water splitting for more than 20 h. The research results in this paper are of great interest to practical applications of the water decomposition process, providing clear and in-depth insights into preliminary robust and efficient multifunctional electrocatalysts for overall water splitting. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the electro-catalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) of synthesized copper tungsten oxide@reduced graphene oxide (CuWO4@rGO) nanocomposites. The prepared CuWO4@rGO nanocomposites show bifunctional electro-chemical performances for the HER and OER via water splitting reactions in alkaline (0.5 M KOH) and acidic (0.5 M H2SO4) media. Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) reveal superlative HER and OER performances of the CuWO4@rGO nanocomposites. The onset over-potentials of the CuWO4@rGO nanocomposites were found to be ∼270 and ∼330 mV for the OER in 0.5 M KOH and 0.5 M H2SO4, respectively, while the onset potentials were found to be ∼180 and ∼135 mV for the HER in 0.5 M KOH and 0.5 M H2SO4, respectively. The CuWO4@rGO nanocomposites also showed lower Tafel slopes of ∼110 and ∼315 mV dec−1 for the OER in 0.5 M KOH and 0.5 M H2SO4, respectively, while the Tafel slopes of the CuWO4@rGO nanocomposites were found to be ∼192 and ∼212 mV dec−1 for the HER in 0.5 M KOH and 0.5 M H2SO4, respectively. Hence, the small energy loss of low-cost electro-catalysts during electro-chemical water splitting reactions reveals comparable HER/OER performances with noble electro-catalysts. [ABSTRACT FROM AUTHOR]

Electrocatalytic overall water splitting is a sustainable method to produce renewable hydrogen energy, but its industrial-scale application is limited by the high energy consumption caused by the high overpotential. Herein, we report the first example of constructing bifunctional cobalt/nitrogen-codoped carbon (CoNC) nanosheet arrays on copper foam (CF) to drive an energy-saving H2 production system with glucose-assisted Cu(I)/Cu(II) redox-looping. A series of size-controllable CoNC nanosheet arrays derived from a ZIF-L precursor are assembled on CF to balance the activity and durability of glucose-assisted Cu(I)/Cu(II) redox-looping and the HER. The optimized CoNC arrays can not only act as a highly-active electrocatalyst of the HER with outstanding electrochemical activity (η10 = 64 mV), but also protect the copper sites of CF from leaching in the glucose-assisted Cu(I)/Cu(II) redox-looping, thus significantly improving the stability of this self-supported electrode. Consequently, a superior energy-saving glucose-assisted system can be assembled by using this bifunctional Cu/CoNC as both the cathode and anode, which exhibits an ultra-low input cell voltage of 0.9 V to achieve 100 mA cm−2 with an ultra-low electricity consumption of 1.97 kW h per cubic meter of H2, much lower than the theoretical value of conventional overall water splitting (1.23 V and 2.7 kW h). [ABSTRACT FROM AUTHOR]