Dewen Wang

Herein, ruthenium (Ru) and iridium (Ir) are introduced to tailor the atomic and electronic structure of self-supported nickel-vanadium (NiV) layered double hydroxide to accelerate water splitting kinetics, and the origin of high hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activities are analyzed at atomic level. X-ray photoelectron spectroscopy and X-ray absorption near-edge structure spectroscopy studies reveal synergistic electronic interactions among Ni, V, and Ru (Ir) cations. Raman spectra and Fourier and wavelet transform analyses of the extended X-ray absorption fine structure indicate modulated local coordination environments around the Ni and V cations, and the existence of V vacancies. The Debye-Waller factor suggests a severely distorted octahedral V environment caused by the incorporation of Ru and Ir. Theoretical calculations further confirm that Ru or Ir doping could optimize the adsorption energy of intermediates in the Volmer and Heyrovsky steps for HER and accelerate the whole kinetic process for OER.

The combinations of Earth-abundant materials with noble metals provide an orientation for developing highly active and stable catalysts toward hydrogen production with reduced noble metal loadings. Here, we designed carbon cloth (CC)-supported Earth-abundant Co(OH)2 nanosheets array (Co(OH)2/CC) as an ideal three-dimensional (3D) substrate for Pt electrodeposition (Pt–Co(OH)2/CC, Pt in Pt–Co(OH)2: 5.7 wt %) to achieve top performance of a hydrogen evolution reaction (HER) under alkaline and neutral conditions. The Pt–Co(OH)2/CC catalyst exhibits a near-zero onset overpotential and a Tafel slope of 70 mV dec–1, and it requires an overpotential of 32, 54, and 122 mV to deliver the geometrical current density of 10, 20, and 100 mA cm–2, respectively, with catalytic activities exceeding to those of the commercial Pt/C decorated CC (Pt/C/CC). Furthermore, the HER activity of Co(OH)2 decorated with several transition metals (Ni, Co, and Fe) was demonstrated in experiments, further validating the high HER activity of the Pt–Co(OH)2/CC catalyst. In addition, this catalyst also offers enhanced catalytic performance and durability under neutral conditions. Impressively, based on the normalized HER current densities by electrochemical surface area, the HER activity of the Pt–Co(OH)2/CC catalyst is 4.8 and 2.6 times greater than that of the commercial Pt/C/CC in alkaline and neutral solution, respectively. The unprecedented catalytic performances of Pt–Co(OH)2/CC catalyst are attributed to the synergistic catalytic effects originating from the nanointerfaces between Co(OH)2 and Pt.