The design of high performance, stable and cost-effective eletrocatalyst for oxygen evolution is crucial for the H2 production from electrochemical water splitting. Here, dual-functional-site catalyst, cobalt-chromium layer double hydroxide (CoCr LDH) nanosheets are designed and synthesized , where the Co 2+ is the catalytic active site and Cr 3+ is the charge transfer site.It's for the first time for OER investigation of CoCr LDH. The CoCr LDH nanosheets have high specific surface area of 151.78 m 2 g -1 and exhibit outstanding OER activities, among the best of Co-based candidates. Accordingly, our catalyst affords a low onset potential of 1.47 V (vs. reversible hydrogen electrode, RHE) and a stable current density of 22.8 mA cm -2 at 1.61 V (vs. RHE) for 12 h. The Tafel slope of CoCr LDH is 81.0 mV dec -1 , smaller than that of state-of-the-art RuO2 (90.1 mV dec -1 ). Therefore, the CoCr LDH nanosheets are promising OER catalysts.
One-dimensional materials favoring efficient charge transfer have attracted enormous attentions. Here cobalt nanochains are prepared by a direct-current (DC) arc-discharge method under the gaseous mixture of He and H 2 . The Co nanochains can range up to several micrometers. When H 2 is replaced by CO 2 , the sample shows a phase evolution from Co nanochains to CoO nanocubes. The ratio of CoO/Co can be effortlessly altered by varying the partial pressure of CO 2 in the reaction gas mixture. CoO nanocubes are attained in the pure CO 2 . The prepared samples are explored as catalyst for oxygen evolution reaction (OER). The catalytic activity is highly dependent on the phase proportion of Co and CoO. The sample prepared under CO 2 :He = 1:7 unveils the optimal OER performance with an onset point of 1.50 V versus reversible hydrogen electrode (RHE) and an overpotential of 350 mV at 10 mA cm −2 . The high OER performance can be attributed to synergistic effect and charge transfer process between Co and CoO. Co can inject electrons into CoO, which manipulates the work function of CoO to make it more suitable for oxygen evolution. The good OER performance can also be ascribed to the defective structure of CoO. The CoO/Co composite shows good robustness with less than 8% current loss throughout the long-term test.
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