It is narrated from Nafi' that when Sayyiduna Abdullah bin Umar (may Allah be pleased with them both) prayed alone, he would recite in all four rak'ahs, reciting Surah al-Fatihah and another surah in every rak'ah, and sometimes in a single rak'ah of an obligatory prayer he would recite two or three surahs. Likewise, in the two rak'ahs of Maghrib he would recite Surah al-Fatihah and one surah each.
Imam al-Shafi'i (may Allah have mercy on him) did not mention Maghrib.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2480