Green synthesis of NiFe LDH/Ni foam at room temperature for highly efficient electrocatalytic oxygen evolution reaction

Abstract

Clean energy technologies such as water splitting and fuel cells have been intensively pursued in the last decade for their free pollution. However, there is plenty of fossil energy consumed in the preparation of the catalysts, which results in a heavy pollution. Therefore, it is much desired but challenging to fabricate high-efficiency catalysts without extra energy input. Herein, we used a facile one-pot room-temperature method to synthesize a highly efficient electrocatalyst of nickel iron layered double hydroxide grown on Ni foam (NiFe LDH/NF) for oxygen evolution reaction (OER). The formation of the NiFe LDH follows a dissolution-precipitation process, in which the acid conditions by hydrolysis of Fe³⁺ combined with NO₃⁻ could etch the NF to form Ni²⁺. Then, the obtained Ni²⁺ was co-precipitated with the hydrolysed Fe³⁺ to in situ generate NiFe LDH on the NF. The NiFe LDH/NF exhibits excellent OER performance with a low potential of about 1.411 V vs. reversible hydrogen electrode (RHE) at a current density of 10 mA cm⁻², a small Tafel slope of 42.3 mV dec⁻¹ and a significantly low potential of ~1.452 V vs. RHE at 100 mA cm⁻² in 1 mol L⁻¹ KOH. Moreover, the material also keeps its original morphology and structure over 20 h. This energy-efficient strategy to synthesize NiFe LDH is highly promising for widespread application in OER catalyst industry.

摘要

绿色能源技术如电解水和燃料电池等由于其无污染的特点, 近年来一直受到人们的广泛关注. 然而, 在合成其催化剂的过程中多会 消耗化石能源, 从而造成环境污染, 形成恶性循环. 因此, 在无额外能量输入的条件下合成高效的电催化剂是非常必要的, 但同时又充满挑 战. 本文通过简单的一步合成法在室温下制备了一种具有高效析氧催化性能的镍铁层状双氢氧化物/泡沫镍(NiFe LDH/NF)催化剂. NiFe LDH的形成遵循溶解-沉淀机理: Fe³⁺水解产生的酸性环境联合NO₃⁻, 刻蚀泡沫镍表面, 形成Ni²⁺, 随后, Ni²⁺与水解的Fe物种原位共沉淀于 泡沫镍表面, 生成NiFe LDH. 所得到的NiFe LDH/NF在碱性环境下, 表现出高效的电催化析氧反应性能. 在1 mol L⁻¹的氢氧化钾溶液中, 当 电流密度为10 mA cm⁻²时, 其电位低至1.411 V vs. RHE, 相应的塔菲尔斜率仅为42.3 mV dec⁻¹, 而在电流密度为100 mA cm⁻²时, 所需电位 也仅为1.452 V vs. RHE. 此外, 该材料还表现出卓越的结构稳定性. 这种绿色制备NiFe LDH/NF的合成方法有望在OER催化中得到广泛的 应用.